Explanation:
A strong electrolyte is defined as the one which contains solute that completely dissociates into ions. Strong acids will lead to the formation of strong electrolytes.
For example, HCl will make a strong electrolyte.
Whereas a weak electrolyte is defined as the one which contains solute that slightly dissociates into ions.
For example, [tex]CH_{3}OH[/tex] is a weak electrolyte.
This is because methanol when dissolved in water does not completely dissociates into ions. Therefore, very less number of ions are present into the solution and as a result, the solution will not be able to conduct electricity.
Also, oxygen atom being more electronegative in nature will hold the hydrogen atom of O-H more tightly, Hence, very less or no hydrogen ions will not present into the solution.
Therefore, we can conclude that methanol is a weak electrolyte.
Methanol, or CH3OH, is classified as a nonelectrolyte because it does not ionize or produce ions when dissolved in water, and can't therefore conduct electricity. In contrast, substances that do dissolve in water to produce ions, and can conduct electricity are electrolytes, either strong or weak.
Explanation:The student question classifies methanol (CH3OH) as a strong electrolyte, a weak electrolyte, or a nonelectrolyte. Methanol would be classified as a nonelectrolyte.
Electrolytes are substances that when dissolved in water, they produce ions. If the process is almost 100% efficient, the substance can be considered a strong electrolyte. If only a small percentage of the substance produces ions, it is a weak electrolyte. However, substances that do not produce ions when dissolved in water are called nonelectrolytes.
Methanol, in this case, does not ionize when dissolved in water, therefore, doesn't produce ions. This classifies it as a nonelectrolyte. This can be further confirmed through a conductance test. Electrolytes can conduct electricity when dissolved in water due to the presence of ions. Since methanol doesn't produce ions when dissolved, it won't conduct electricity, substantiating its classification as a nonelectrolyte.
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Which is more stable hydroxyl isopropyl or benzhydrol radical?
The benzhydrol radical is more stable than the hydroxyl isopropyl radical because it can delocalize its unpaired electron through resonance across the aromatic ring, while the hydroxyl isopropyl radical lacks such extensive resonance stabilization.
When considering the stability of hydroxyl isopropyl and benzhydrol radicals, it's important to look at resonance stabilization. Radicals that can delocalize their unpaired electron through resonance are generally more stable. In the case of a benzhydrol radical, also known as a benzylic radical, there is significant stabilization due to the possibility of multiple resonance structures. This is because the unpaired electron in the benzhydrol radical can be delocalized through the aromatic ring's system of conjugated pi bonds.
On the other hand, the hydroxyl isopropyl radical, which is an alkyl radical, lacks the extended conjugated system that allows for such delocalization. While it may have some hyperconjugative stabilization, it does not benefit from the extensive resonance stabilization that the benzhydrol radical enjoys. As such, the benzhydrol radical is more stable than the hydroxyl isopropyl radical due to the resonance effects and the subsequent delocalization of the unpaired electron across the aromatic ring.
What is the mass of 1 mole of Pb?
Answer:
207.2 g
Explanation:
The mass of 1 mole of lead is given by its molar mass, which is 207.2 g/mol. This is an average molar mass, corresponding to the weighted average of the 4 lead isotopes, ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb, considering their abundance in nature. The mass of 1 mole of Pb is:
1 mol × (207.2 g/mol) = 207.2 g
How many neutrons are found in Cr-54
Answer:
30
Explanation:
To find out the neutron number of an element we must first know what the mass value of that element is and the value of the atom number of that element. To find out these values, just look for the element in the periodic table. Once discovered simply subtract the values using the formula:
No. of neutrons = mass - atom number.
In the case of Cr, the mass is 54, while the atom number is 24. So we can find the number of neutrons.
Cr Neutrons = 54-24 = 30
If kc = 7.04 × 10-2 for the reaction: 2 hbr(g) ⇌h2(g) + br2(g), what is the value of kc for the reaction: 1/2 h2(g) + 1/2 br2 ⇌hbr(g)
The value of Kc for the second reaction is mathematically given as
Kc' = 3.769
What isthe value of Kc for the second reaction?
Question Parameters:
kc = 7.04 × 10-2 for the reaction
2 hbr(g) ⇌h2(g) + br2(g)
1/2 h2(g) + 1/2 br2 ⇌hbr(g)
Generally, the equation for the reaction is mathematically given as
2HBr(g) ⇄ H2(g) + Br2(g)
Therefore
Kc = [H2] [Br2] / [HBr]^2
7.04X10^-2 = [H2][Br] / [HBr]^2
Upon final reaction
Kc' = [HBr] / [H2]^1/2*[Br2]^1/2
Hence
[tex]\sqrt{(1/7.04X10^-2)}= [HBr] / [H2]^1/2*[Br]^1/2}\\\\Kc' = \sqrt{(1/7.04X10^-2)[/tex]
Kc' = 3.769
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Consider the reaction a + b c +
d. at biochemical equilibrium (25°c, ph of 7), the concentration of a is 0.2 m, the concentration of b is 0.2 m, the concentration of c is 0.8 m, and the concentration of d is 0.8 m. calculate δg and δg° ′ under these conditions.
Many drugs decompose in blood by a first-order process. two tablets of aspirin supply 0.60 g of the active compound. after 30 min, this compound reaches a maximum concentration of 2 mg/100 ml of blood. if the half-life for its breakdown is 90 min, what is its concentration (in mg/100 ml) 4.0 h after it reaches its maximum concentration?
The concentration of drug after 4.5 hoursis [tex]\boxed{{\text{0}}{\text{.25 mg/100 mL}}}[/tex].
Further Explanation:
Radioactive decayis responsible to stabilizeunstable atomic nucleusaccompanied by the release of energy.
Half-life is the duration after which half of the original sample has been decayed and half is left behind. It is represented by [tex]{t_{{\text{1/2}}}}[/tex].
The relation between rate constant and half-life period for first-order reaction is as follows:
[tex]k = \dfrac{{0.693}}{{{t_{{\text{1/2}}}}}}[/tex] …… (1)
Here,
[tex]{t_{{\text{1/2}}}}[/tex] is half-life period.
k is rate constant.
Substitute 90 min for [tex]{t_{{\text{1/2}}}}[/tex] in equation (1).
[tex]\begin{aligned}k &= \frac{{0.693}}{{90{\text{ min}}}} \\&= 7.7 \times {10^{ - 3}}{\text{ mi}}{{\text{n}}^{ - 1}} \\\end{aligned}[/tex]
Radioactive decay formula is as follows:
[tex]{\text{A}} = {{\text{A}}_0}{e^{ - kt}}[/tex] …… (2)
Here
A is the concentration of sample after time t.
t is the time taken.
[tex]{{\text{A}}_0}[/tex] is the initial concentration of sample.
k is the rate constant.
The time for the process is to be converted into min. The conversion factor for this is,
[tex]1{\text{ hr}} = 60\min[/tex]
Therefore time taken can be calculated as follows:
[tex]\begin{aligned}t&= \left( {4.5{\text{ hr}}} \right)\left( {\frac{{60{\text{ min}}}}{{1{\text{ hr}}}}} \right) \\&= 270{\text{ min}} \\\end{aligned}[/tex]
Substitute 2 mg/100 mL for [tex]{{\text{A}}_0}[/tex] , [tex]7.7 \times {10^{ - 3}}{\text{ mi}}{{\text{n}}^{ - 1}}[/tex] for k and 270 min for t in equation (2).
[tex]\begin{aligned}{\text{A}} &= \left( {\frac{{2{\text{ mg}}}}{{100{\text{ mL}}}}} \right){e^{ - \left( {7.7 \times {{10}^{ - 3}}{\text{ mi}}{{\text{n}}^{ - 1}}} \right)\left( {270{\text{ min}}} \right)}} \\&= \frac{{0.25{\text{ mg}}}}{{100{\text{ mL}}}} \\\end{aligned}[/tex]
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Answer details:
Grade: Senior School
Subject: Chemistry
Chapter: Radioactivity
Keywords: half-life, 0.25 mg/100 mL, 2 mg/100 mL, A, k, t, rate constant, 4.5 h, 270 min, radioactive decay formula.
What does R stand for in ideal gas law?
In the Ideal Gas law, the letter R represents the universal gas constant. Its value depends on the units being used for pressure, volume, moles, and temperature. The ideal gas law equation is PV=nRT.
Explanation:In the Ideal Gas law, the letter R stands for the universal gas constant. This constant is derived from the Ideal Gas Equation: R = 0.08206 L atm mol-¹ K-¹ or 8.314 L kPa mol-¹ K-¹. The ideal gas law itself is represented as PV = nRT, where P represents pressure, V is volume, n is the number of moles of the gas, T is temperature in Kelvin, and R is the universal gas constant.
The value of R, 0.08206 L atm mol-¹ K-¹ or 8.314 J/mol · K, depends on the units being used. For instance, when using SI units, R would be 8.31 J/mol · K.
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Approximately how many moles of boron make up 1.20 × 10^24 atoms of boron?
A. 7.22 × 10^47 moles
B. 6.02 × 10^23 moles
C. 5.00 moles
D. 1.99 moles
You used both HNO3 and H2SO4 solutions in this experiment. briefly answer the following question.
why couldn't you substitute 3M H2SO4 for concentrated HNO3 in Part 1?
You couldn't substitute 3M H2SO4 for concentrated HNO3 in Part 1 of the experiment due to the significant differences in their reactivity and properties. HNO3 is a powerful oxidizing agent and provides specific reactions, while H2SO4 is a strong acid but not as strong an oxidizing agent.
Explanation:The reason you couldn't substitute 3M H2SO4 for concentrated HNO3 in Part 1 of the experiment is due to the difference in their reactivity and properties. Nitric Acid (HNO3) is a powerful oxidizing agent. This means it has the ability to oxidize other substances, bringing about specific chemical reactions. On the other hand, Sulfuric Acid (H2SO4), while still a strong acid, is not as strong an oxidizing agent and would not yield the same results if used as a substitute for HNO3 in this experiment.
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What is the smallest particle of an element that still retains all the properties of the element? a compound a mineral an atom an isotope
The basic building block of chemistry is known as the atom. The smallest particle of an element that still retains all the properties of the element is known as the atom. The correct option is C.
What is an atom?The atom can be considered as the basic building blocks of matter which possess the properties of the chemical element. An atom don't exist independently, instead they form ions and molecules which in turn combine in large numbers to form matter.
An atom is an indivisible particle and it contains the sub-atomic particles like protons, electrons and neutrons. The positively charged particles are called protons, the negatively charged particles are called electrons. The neutrons are chargeless particles.
All atoms of the same element are identical but different elements have different types of atoms. The chemical reactions occur when the atoms are rearranged.
Thus the correct option is C.
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Match the each term with its definition. 1) reaction coordinate a) the higher point on the energy curve 2) δg° b) the plot of the reaction progress as a function of time 3) δg‡ c) the free energy of the reaction
H2+I2= 2HI+3 kcal Based on the reaction given above, as the temperature decreases, the formation of the reactants will: A. decrease B. increase C. remained consistent D. indeterminate
the answer is A: decrease
Water is a polar molecule, meaning it carries partial charges (δ or δ–) on opposite sides of the molecule. for two formula units of kbr, drag two potassium ions and two bromide ions to where they would most likely appear based on the grouping of the water molecules in the area provided.
[tex]{{\mathbf{K}}^{\mathbf{+}}}[/tex] will be dragged towards the side of [tex]{\mathbf{O}}{{\mathbf{H}}^{\mathbf{-}}}[/tex] while [tex]{\mathbf{B}}{{\mathbf{r}}^{\mathbf{-}}}[/tex] will be dragged towards the side of [tex]{{\mathbf{H}}^{\mathbf{+}}}[/tex]. (Refer to the attached image)
Further explanation:
Electronegativity:
It is defined as the tendency of an atom to attract the shared electrons in the bond towards itself is known as electronegativity. The more electronegative atom will more attract the bonding electrons towards itself than the less electronegative one. Therefore the electrons will spend more time with the more electronegative atom than an electropositive atom. The electronegative atom will acquire the partial negative charge, and the electropositive atom will acquire a partial positive charge.
The polarity of the bond can be estimated by the electronegativity difference [tex]\left({\Delta {\text{EN}}}\right)[/tex]. [tex]\Delta{\text{EN}}[/tex]is the electronegativity difference between the two atoms that are bonded to each other. The formula to calculate [tex]\Delta{\text{EN}}[/tex]in XY bond is as follows:
[tex]{\mathbf{\Delta EN=}}\left({{\mathbf{electronegativity of Y}}} \right){\mathbf{-}}\left({{\mathbf{electronegativity of X}}}\right)[/tex]
Here, X is the electropositive atom and Y is the electronegative atom.
Higher the electronegativity difference between the two atoms, more will be the polarity of the bond and vice-versa.
Water is a polar molecule. Hydrogen atom acquires partial positive charge while oxygen atom is partially negatively charged. So the end of the water molecule with hydrogen is positively charged, and that with oxygen is negatively charged.
In the case of a potassium-bromine bond, bromine is more electronegative than potassium. So the electrons will be more attracted towards bromine due to which it develops a partial negative charge. Potassium, being less electronegative than bromine, in turn, acquires a partial positive charge. This separation of charge results in the formation of a polar bond between potassium and bromine.
So [tex]{{\text{K}}^+}[/tex] will be dragged towards the side of [tex]{\text{O}}{{\text{H}}^-}[/tex] while [tex]{\text{B}}{{\text{r}}^-}[/tex] will be dragged towards the side of [tex]{{\text{H}}^+}[/tex].
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Answer details:
Grade: Senior School
Subject: Chemistry
Chapter: Covalent bonding and molecular structure
Keywords: electronegativity difference, electropositive, electronegative, electrons, polar, KBr, K, Br, K+, Br-, H+, OH-, potassium, bromine, hydrogen, oxygen.
If a propane heater burns 38.95 g C3H8, it consumes 38.95 mol C3H8. 0.8830 mol C3H8. 1 mol C3H8. 44.10 mol C3H8.
Answer:
Option-2 (0.8830 mol C₃H₈) is the correct answer.
Solution:
In statement we are given with the amount of propane gas and are asked to find out the moles for given mass.
As we know mass is related to moles as follow,
Moles = Mass / M.mass ----- (1)
Data Given:
Moles = ??
Mass = 38.95 g
M.mass = (C)3 + (H)8 = (12)3 + (1)8 = 36 + 8 = 44 g/mol
Putting values in equation 1,
Moles = 38.95 g / 44 g/mol
Moles = 0.8854 Moles
In an experiment, you combine 83.77 g of iron with an excess of sulfur and then heat the mixture to obtain iron(III) sulfide. 2Fe(s) + 3S(s) → Fe2S3(s) What is the theoretical yield, in grams, of iron(III) sulfide?
The theoretical yield of iron (II) sulfide would be 155.92 g
Theoretical yieldIt is the total stoichiometric product from a reaction.
From the equation of the reaction:
2Fe(s) + 3S(s) → Fe2S3(s)
The mole ratio of Fe to Fe2S3 is 2:1
Mole of 83.77 g Fe = 83.77/55.85
= 1.4999 moles
Equivalent mole of Fe2S3 = 1.4999/2
= 0.75 moles
Mass of 0.75 mole Fe2S3 = 0.75 x 207.9
= 155.92 g
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Draw the acetal produced when ethanol adds to ethanal.
Explanation:
Acetals are geminal diethers derivatives of aldehyde formed by the addition to equivalent molecules of an alcohol and removal of water.
When ethanol is added to the ethanal in acidic medium:
Ethanal + Ethanol → Hemiacetal
Hemiacetal + Ethanol → Acetal
Acetal produced when ethanol is added to ethanal are given in the image attached.
Scientists often investigate alternative explanations for the data and observations presented, even once a hypothesis has been tested and supported through an experiment. This investigation of alternative explanations ...
Answer:
Strengthens the evidence and support for a scientific theory.
Explanation:
Hello,
Scientific method provides a compelling tool scientists use to both develop and demonstrate new theories. As it involves both the observation and experimentation towards a specific subject of matter, it turns out convenient to consider alternative explanations substantiating such subject of matter in light of obtaining a more precise explanation for it. In such a way, this investigation of alternative explanations strengthens the evidence and support for a scientific theory.
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Which of these carbohydrates is a monosaccharide maltose fructose cellulose or lactose
Which of the following is a part of a land based carbon cycle ?coral reefs
Crab shells
Trees
Whales
Answer:
c
Explanation:
using the equation 2H2+O2-->2H2O if 19g of oxygen reacts completely, how many grams of hydrogen must react with it
Answer: 2.4 grams
Explanation:
To calculate the moles, we use the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex]
For [tex]O_2[/tex]
Given mass = 19 g
Molar mass of [tex]O_2[/tex] = 32 g/mol
Putting values in above equation, we get:
[tex]\text{Moles of}O_2=\frac{19}{32}=0.60moles[/tex]
[tex]2H_2+O_2\rightarrow 2H_2O[/tex]
1 mole of [tex]O_2[/tex] reacts with 2 moles of [tex]H_2[/tex]
0.60 moles of [tex]O_2[/tex] wil react with =[tex]\frac{2}{1}\times 0.60=1.20[/tex] moles of [tex]H_2[/tex]
mass of [tex]H_2=moles\times {\text {molar mass}}=1.20moles\times 2g/mol=2.4g[/tex]
Thus 2.4 grams of hydrogen will react completely with 19 g of oxygen.
H2o is the chemical formula for water. in order to produce a single molecule of water, how many hydrogen atoms are needed?
Final answer:
To produce a single molecule of water (H₂O), exactly two hydrogen atoms are required. This 2:1 ratio of hydrogen to oxygen atoms is consistent no matter how many molecules of water are being made.
Explanation:
To produce a single molecule of water, which has the chemical formula H₂O, you need two hydrogen atoms. The subscript '2' in H₂ indicates that there are two hydrogen atoms for every oxygen atom in a water molecule. Therefore, for each molecule of water you create, you must have this 2:1 ratio of hydrogen to oxygen atoms.
For example, if you want to create two water molecules, you would need a total of 4 hydrogen atoms (2 molecules × 2 atoms/molecule). Similarly, to produce five water molecules, you would require 10 hydrogen atoms in all (5 molecules × 2 atoms/molecule). No matter the number of water molecules you are looking to produce, you will always need twice as many hydrogen atoms as you have water molecules because of this consistent ratio.
Experimental data have shown that the rate law for the reaction 2 hgcl2(aq) + c2o4 2 -(aq) → 2 cl-(aq) + 2 co2 (g) + hg2cl2 (s) is: rate = k[hgcl2][c2o4 2 -]2 how will the rate of reaction change if the concentration of c2o4 2 - is tripled and the concentration of hgcl2 is doubled?
Answer:
The rate will be doubled by a Factor of 18
Explanation:
Good luck to everyone doing this!! you got this
The rate of the reaction will increase by a factor of 18 if the concentration of C2O42- is tripled and the concentration of HgCl2 is doubled.
Explanation:The question asks how the rate of the reaction 2 HgCl2(aq) + C2O42-(aq) → 2 Cl-(aq) + 2 CO2 (g) + Hg2Cl2 (s) will change if the concentration of C2O42- is tripled and the concentration of HgCl2 is doubled. Given the rate law rate = k[HgCl2][C2O42-]2, we can predict the effect on the rate. If the rate law is followed, tripling [C2O42-] will increase the rate by a factor of 32 or 9 because the concentration of C2O42- is squared in the rate law. Doubling [HgCl2] will double the rate of reaction. Therefore, tripling [C2O42-] and doubling [HgCl2] together will increase the reaction rate by a factor of 2 * 9 = 18.
Use the periodic table in the tools bar to complete the electron configurations for the following elements: Lithium (Li): 1sA2sB
Answer: Value of A is 2 and value of B is 1.
Explanation:
Lithium is the third element of the periodic table. It belongs to the Period 2 and Group 1 and is considered as an alkali metals.
To write the electronic configuration, we need to find the number of electrons this element contain, which is equal to the atomic number.
Number of electrons = Atomic number = 3
So, the electronic configuration will be: [tex]1s^22s^1[/tex]
The s-orbital in total can contain only 2 electrons.
Hence, the value of A is 2 and value of B is 1.
The periodic table showcases the table of the chemical elements listed in order of atomic number, usually in rows(period) from the left to the right, in such a way that elements with similar atomic structures as well as similar chemical properties can be located in vertical columns (groups).
Lithium is the third chemical element on the periodic table. It can be located on group 1 element also known as the alkali metals. It is soft in nature and has a whitish color.
The electronic configuration explains how electrons are distributed in their atomic orbitals.
The electronic configuration for Lithium can be expressed as:
Li: 1s² 2s¹
Therefore, from the given information, we can conclude that the value for the electronic configuration of A and B in the Lithium sample given is 2 and 1 respectively
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What products are formed from monochlorination of (2r)−2−bromobutane at c1 and c4? draw the products using skeletal structures?
Which of the following could be classified as matter? Check all of the boxes that apply. desk water idea cloud helium dream
Examples of matter include;
DeskWaterCloudHeliumFurther ExplanationMatter Matter is anything that has weight and occupies space. Matter exists in three states, liquid, gases, and solids.For example, from the examples above; helium is matter in a gaseous state, water in liquid state and desk in solid-state.Matter is made up of small particles that are in continuous random movement.Particles A particle refers to a single atom or a group of atoms that are bonded together and functions as a single unit. Therefore, matter is made up of particles that can either be single atoms or chemically bonded atoms to make a molecule. Hence, a molecule is also a particle of matter.An atom An atom is the smallest particle of an element that can take part in a chemical reaction.Atoms are made up of sub-atomic particles which include; protons, neutrons, and electrons. When two or more atoms are bonded together they form a molecule.Molecule A molecule is the smallest particle of an element or a compound that has similar properties of that particular compound or element.Molecules could be made up of atoms that are similar such as oxygen molecules or atoms that different from different elements, such as water molecules.The bonding of atoms to form molecules occurs as a result of the sharing or transfer of electrons between atoms.Keywords: Matter, states of matter, particles, atoms, molecules, elements, compounds
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Subject: Chemistry
Topic: Matter and particles of matter
Sub-topic: Classification of matter
Explain why c6h5ch2ch2br is not formed during the radical bromination of c6h5ch2ch3. select the single best answer.
Final answer:
C6H5CH2CH2Br is not formed during the radical bromination of C6H5CH2CH3 because the intermediate benzyl radical, formed at the carbon adjacent to the aromatic ring, is much more stable than the primary radical needed for the other product. Selectivity is due to bromine's preference for stable radicals, supported by Hammond's postulate.
Explanation:
The reason why C6H5CH2CH2Br is not formed during the radical bromination of C6H5CH2CH3 involves the relative stability of the radical intermediate. Radical bromination tends to occur at the position that forms the most stable radical, which for a benzyl compound is the carbon atom directly adjacent to the aromatic ring. The radical formed at this position, a benzyl radical, is highly stabilized by resonance. In contrast, the radical that would be required to form C6H5CH2CH2Br is a primary radical, which is less stable and thus less likely to form. This selectivity is due to the fact that bromine radicals are relatively selective and prefer to abstract hydrogen atoms from positions that lead to more stable radical intermediates. Moreover, Hammond's postulate suggests that since the radical formation with bromine is endothermic, the transition state will more closely resemble the stable radical intermediate, leading to more selective radical formation.
You are given a crushed sample that is a mixture of limestone (caco3), lime (cao), and sand. the calcium carbonate, limestone, is the only material present in the material that will decompose when heated. you subject a 6.4734 g sample of the mixture to strong heating and after the sample reaches a constant mass (no more mass is lost with additional heating), the sample has a final weight of 4.3385 g. what is the percentage of calcium carbonate present in the original mixture? (f.wt. caco3 = 100.1)
A mysterious white powder could be powdered sugar (C12H22O11), cocaine (C17H21NO4), codeine (C18H21NO3), norfenefrine (C8H11NO2), or fructose (C6H12O6). When 82 mg of the powder is dissolved in 1.50 mL of ethanol (d = 0.789 g/cm3, normal freezing point −114.6 ∘C, Kf = 1.99 ∘C/m), the freezing point is lowered to −115.5 ∘C. What is the identity of the white powder?
Norfenefrine (C₈H₁₁NO₂).
Further explanationWe will solve a case related to one of the colligative properties, namely freezing point depression.
The freezing point of the solution is the temperature at which the solution begins to freeze. The difference between the freezing point of the solvent and the freezing point of the solution is called freezing point depression.
[tex]\boxed{ \ \Delta T_f = T_f(solvent) - T_f(solution) \ } \rightarrow \boxed{ \ \Delta T_f = K_f \times molality \ }[/tex]
Given:
A mysterious white powder could be,
powdered sugar (C₁₂H₂₂O₁₁) with a molar mass of 342.30 g/moles, cocaine (C₁₇H₂₁NO₄) with a molar mass of 303.35 g/moles, codeine (C₁₈H₂₁NO₃) with a molar mass of 299.36 g/moles, norfenefrine (C₈H₁₁NO₂) with a molar mass of 153.18 g/moles, or fructose (C₆H₁₂O₆) with a molar mass of 180.16 g/moles.When 82 mg of the powder is dissolved in 1.50 mL of ethanol (density = 0.789 g/cm³, normal freezing point −114.6°C, Kf = 1.99°C/m), the freezing point is lowered to −115.5°C.
Question: What is the identity of the white powder?
The Process:
Let us identify the solute, the solvent, initial, and final temperatures.
The solute = the powderThe solvent = ethanolThe freezing point of the solvent = −114.6°CThe freezing point of the solution = −115.5°CPrepare masses of solutes and solvents.
Mass of solute = 82 mg = 0.082 gMass of solvent = density x volume, i.e., [tex]\boxed{ \ 0.789 \ \frac{g}{cm^3} \times 1.50 \ cm^3 = 1.1835 \ g = 0.00118 \ kg \ }[/tex]We must prepare the solvent mass unit in kg because the unit of molality is the mole of the solute divided by the mass of the solvent in kg.
The molality formula is as follows:
[tex]\boxed{ \ m = \frac{moles \ of \ solute}{kg \ of \ solvent} \ } \rightarrow \boxed{ \ m = \frac{mass \ of \ solute \ (g)}{molar \ mass \ of \ solute \times kg \ of \ solvent} \ }[/tex]
Now we combine it with the formula of freezing point depression.
[tex]\boxed{ \ \Delta T_f = K_f \times \frac{mass \ of \ solute \ (g)}{molar \ mass \ of \ solute \times kg \ of \ solvent} \ }[/tex]
It is clear that we will determine the molar mass of the solute (denoted by Mr).
We enter all data into the formula.
[tex]\boxed{ \ -114.6^0C - (-115.5^0C) = 1.99 \frac{^0C}{m} \times \frac{0.082 \ g}{Mr \times 0.00118 \ kg} \ }[/tex]
[tex]\boxed{ \ 0.9 = \frac{1.99 \times 0.082}{Mr \times 0.00118} \ }[/tex]
[tex]\boxed{ \ Mr = \frac{0.16318}{0.9 \times 0.00118} \ }[/tex]
We get [tex]\boxed{ \ Mr = 153.65 \ }[/tex]
These results are very close to the molar mass of norfenefrine which is 153.18 g/mol. Thus the white powder is norfenefrine.
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The identity of the white powder is [tex]\boxed{\text{norfenefrine}(\text{C}_{8}\text{H}_{11}\text{NO}_{2})}[/tex] .
Further Explanation:
Colligative properties
These are the properties that depend on the number of solute particles and not on their mass or identities. Following are the four colligative properties:
1. Relative lowering of vapor pressure
2. Elevation in boiling point
3. Depression in freezing point
4. Osmotic pressure
The temperature where a substance in its liquid form is converted into the solid state is known as freezing point. Freezing point depression is a colligative property because it depends on the number of moles of solute particles.
The expression for the freezing point depression is as follows:
[tex]\Delta\text{T}_\text{f}=\text{K}_\text{f}\,\text{m}[/tex] …… (1)
Here,
[tex]\Delta\text{T}_\text{f}[/tex] is the depression in freezing point.
[tex]\text{K}_\text{f}[/tex] is the cryoscopic constant.
m is the molality of the solution.
The formula to calculate the density of substance is as follows:
[tex]\text{Density of substance}=\dfrac{\text{Mass of substance}}{\text{Volume of substance}}[/tex] …… (2)
Rearrange equation (2) for the mass of substance.
[tex]\text{Mass of substance}=(\text{Density of substance })(\text{Volume of substance})[/tex] …… (3)
The volume of the substance is to be converted into . The conversion factor for this is,
[tex]1\,\text{ml}=1\,\text{cm}^3[/tex]
Therefore the volume of the substance can be calculated as follows:
[tex]\begin{aligned}\text{Volume}&=(1.50\,\text{mL})\left(\frac{1\,\text{cm}^3}{1\,\text{mL}}\right)\\&=1.50\,\text{cm}^3\end{aligned}[/tex]
Substitute [tex]1.50\,\text{cm}^3[/tex] for the volume of substance and [tex]0.789\,\text{g/gm}^3[/tex] for the density of the substance in equation (3) to calculate the mass of solvent.
[tex]\begin{aligned}\text{Mass of solvent}&=\left(\dfrac{0.789\,\text{g}}{1\,\text{cm}^3}\right)(1.50\,\text{cm}^3)\\&=1.1835\,\text{g}\end{aligned}[/tex]
This mass is to be converted into kg. The conversion factor for this is,
[tex]1\,\text{g}=10^{-3}\,\text{kg}[/tex]
Therefore the mass of solvent can be calculated as follows:
[tex]\begin{aligned}\text{Mass of solvent}&=(1.1835\,\text{g})\left(\dfrac{10^{-3}\,\text{kg}}{1\,\text{g}}\right)\\&=0.0011835\,\text{kg}\end{aligned}[/tex]
The mass of solute is to be converted into g. The conversion factor for this is,
[tex]1\,\text{mg}=10^{-3}\,\text{g}[/tex]
Therefore the mass of solute can be calculated as follows:
[tex]\begin{aligned}\text{Mass of solute}&=(82\,\text{mg})\left(\dfrac{10^{-3}\,\text{g}}{1\,\text{g}}\right)\\&=0.082\,\text{g}\end{aligned}[/tex]
The freezing point depression can be calculated as follows:
[tex]\begin{aligned}\Delta\text{T}_\text{f}&=-114.6\,^\circ\text{C}-(-115.5\,^\circ\text{C})\\&=0.9\,\circ\text{C}\end{aligned}[/tex]
The formula to calculate the molality of solution is as follows:
[tex]\text{Molality of solution}=\dfrac{\text{Amount (mol) of solute}}{\text{Mass (kg) of solvent}}[/tex] …… (4)
The formula to calculate the amount of solute is as follows:
[tex]\text{Amount of solute}=\dfrac{\text{Mass of solute}}{\text{Molar mass of solute}}[/tex] …… (5)
Incorporating equation (5) into equation (4),
[tex]\text{Molality of solution}=\dfrac{\text{Mass of solute}}{(\text{Mass of solvent})(\text{Molar mass of solute})}[/tex] …… (6)
Incorporating equation (6) into equation (1),
[tex]\Delta\text{T}_\text{f}=\text{k}_\text{f}\left(\dfrac{\text{Mass of solute}}{(\text{Mass of solvent})(\text{Molar mass of solute})}\right)[/tex] …… (7)
Rearrange equation (7) to calculate the molar mass of solute.
[tex]\text{Molar mass of solute}=\dfrac{\text{k}_\text{f}}{\Delta\text{T}_\text{f}}\left(\dfrac{\text{Mass of solute}}{\text{Mass of solvent}}\right)[/tex] …… (8)
Substitute [tex]1.99\,^\circ\text{C/m}[/tex] for [tex]\text{k}_\text{f}[/tex], [tex]0.9\,^\circ\text{C}[/tex] for [tex]\Delta\text{T}_\text{f}[/tex], 0.082 g for the mass of solute and 0.0011835 kg for the mass of solvent in equation (8).
[tex]\begin{aligned}\text{Molar mass of solute}&=\left(\dfrac{1.99}{0.9}\right)\left(\dfrac{0.082}{0.0011835}\right)\\&=153.199\,\text{g/mol}\\&=\approx153.2\,\text{g/mol}\end{aligned}[/tex]
The molar mass of powdered sugar is 342.3 g/mol.
The molar mass of cocaine is 303.4 g/mol.
The molar mass of codeine is 299.4 g/mol.
The molar mass of norfenefrine is 153.2 g/mol.
The molar mass of fructose is 180.2 g/mol.
The calculated molar mass of solute is similar to that of norfenefrine. So the identity of the white powder is norfenefrine.
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Grade: Senior School
Chapter: Solutions
Subject: Chemistry
Keywords: colligative properties, depression in freezing point, cryoscopic constant, freezing point, 153.199 g/mol, norfenefrine.
For a particular first-order reaction, it takes 3.0 minutes for the concentration of the reactant to decrease to 25% of its initial value. what is the value for rate constant (in s-1) for the reaction?
For a first-order reaction, the rate constant can be determined using the concentration of the reactant at a given time. In this case, the rate constant is 0.25 s^-1.
Explanation:A first-order reaction is one in which the rate of reaction is directly proportional to the concentration of the reactant. The rate law expression for a first-order reaction is given by rate = k[A], where [A] is the concentration of the reactant and k is the rate constant.
In this case, the concentration of the reactant decreases to 25% of its initial value in 3.0 minutes. We can use this information to determine the rate constant (k).
25% of the initial concentration corresponds to 0.25 times the initial concentration, so the concentration at that time is 0.25[A]. We can substitute this value into the rate law expression and solve for k:
0.25[A] = k[A]
0.25 = k
Therefore, the value for the rate constant (k) for the reaction is 0.25 s-1.
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To find the rate constant (k) for a first-order reaction, we can use the half-life formula. The given information states that it takes 3.0 minutes for the concentration of the reactant to decrease to 25% of its initial value. By substituting these values into the equation, we can find the rate constant.
Explanation:To determine the rate constant (k) for the first-order reaction, we can use the formula for the half-life of a first-order reaction. The half-life is the amount of time it takes for the concentration of the reactant to decrease to half of its initial value. In this case, it takes 3.0 minutes for the concentration to decrease to 25% of its initial value, which is equivalent to one half-life.
The formula for the first-order half-life is: t1/2 = ln(2)/k
Since the concentration decreases to 25% of its initial value after one half-life, we can use this information to solve for k:
25% = (1/2) * 100% = e-kt1/2
ln(1/2) = -k * t1/2
k = -ln(1/2) / t1/2
Substituting the given values, we have:
k = -ln(1/2) / 3.0 minutes
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Seafloor spreading provides evidence of which of the following Earth processes?
A.erosion of coastlines
B.weathering of mountains
C.movement of crustal plates
D.formation of sedimentary rocks
Seafloor spreading provides evidence for D. formation of sedimentary rocks.
Seafloor spreading occurs when there's volcanic activity that leads to the formation of a new oceanic crust. Sedimentary rocks refer to the rocks that are formed when there's an accumulation of organic particles or minerals on the surface of the Earth.It should be noted that sedimentary rocks are deposited in layers that are referred to as strata. Examples of sedimentary rocks include limestones, iron ore, chert, etc.In conclusion, when seafloor spreading occurs, there are sediments that overtime accumulates and forms sedimentary rock.
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