Answer:
0.952 °C
Explanation:
The change in melting point is computed as:
ΔT = k*m*i
where ΔT is the difference between the melting point of water and of solution, k is a constant (1.86 °C*kg/mol for water), i is the van't Hoff factor (equal to 2 for sodium chloride because 2 ions are obtained after its dissolution), and m is the molality of the solution.
Molar mass of sodium chloride: 58.44 g/mol
Moles of of sodium chloride: mass / molar mass 3.5/58.44 = 0.059 mol
Density of water 1 kg/L
230 mL of water are equivalent to 0.23 L
mass of water: density * volume = 1*0.23 = 0.23 kg
Molality of the solution: m = moles of solute/ kg of solvent = 0.059/0.23 = 0.256
Finally:
ΔT = 1.86*0.256*2 = 0.952 °C
Water melting point: 0 °C
So, the solution melting point is: 0 - 0.952 = 0.952 °C
Which acid dissociation constant (ka indicates the weakest acid? 8.5 × 10–3m 1.5 × 10–10m 3.5 × 10–7m 5.1 × 10–5m?
Which of the following chemical equations is correctly balanced?
A.) H2 + O2 → H2O
B.) 2 C2H4O + 5 O2 → 4 CO2 + 4 H2O
C.) K2S + I2 → 2 KI + S
D.) CaCO3 + 2 HCl → CaCl2 + 2 CO2 + H2O
Option B and C both are balanced.
A chemical reaction is said to be balanced if all the constituent on the left side of the reaction arrow are equal to right side.
(A) The chemical reaction is as follows:
[tex]H_{2}+O_{2}\rightarrow H_{2}O[/tex]
There are 2 hydrogen atoms and 2 oxygen atoms on left side of the reaction arrow and 2 hydrogen and 1 oxygen on right hand side thus, number of oxygen atoms are not balanced.
Therefore, the above chemical reaction is not balanced.
(B) The chemical reaction is as follows:
[tex]2C_{2}H_{4}O+5O_{2}\rightarrow 4CO_{2}+4H_{2}O[/tex]
There are 4 carbon atoms, 8 hydrogen atoms and 12 oxygen atoms on both side of the reaction arrow thus, the chemical reaction is balanced.
(C) The chemical reaction is as follows:
[tex]K_{2}S+I_{2}\rightarrow 2KI+S[/tex]
There are 2 potassium atoms, 1 sulfur atom and 2 iodine atoms on both side of the reaction arrow thus, it is a balanced chemical reaction.
(D) The chemical reaction is as follows:
[tex]CaCO_{3}+2HCl\rightarrow CaCl_{2}+2CO_{2}+H_{2}O[/tex]
There is 1 calcium atom, 1 carbon atom, 3 oxygen atoms, 2 hydrogen atoms and 2 chlorine atoms on left side of the reaction arrow and 1 calcium atom, 2 chlorine atoms, 2 carbon atoms, 5 oxygen atoms and 2 hydrogen atoms on right hand side of the reaction arrow. Thus, number of carbon and oxygen atoms are not balanced in the chemical reaction.
A balanced chemical reaction has the same and a balanced number of stoichiometry coefficients. Option B. [tex]\rm 2 C_{2}H_{4}O + 5 O_{2} \rightarrow 4 CO_{2} + 4 H_{2}O[/tex] and option D. [tex]\rm K_{2}S + I_{2} \rightarrow 2 KI + S[/tex] are balanced equations.
What is a balanced chemical reaction?A balanced chemical reaction is the equated reaction and depiction of the chemical reactants and the products of the reaction. They have balanced stoichiometry coefficients on the left and the right side of the reaction.
In the second reaction, [tex]\rm 2 C_{2}H_{4}O + 5 O_{2} \rightarrow 4 CO_{2} + 4 H_{2}O[/tex], the number of carbon atoms are four on both sides, 8 atoms of hydrogen on both sides and 12 atoms of oxygen balanced on both sides of the chemical reaction.
In the third reaction, [tex]\rm K_{2}S + I_{2} \rightarrow 2 KI + S[/tex], 2 atoms of potassium, 2 atoms of iodine and 1 atom of sulphur is balanced.
Therefore, reactions B and D are balanced reactions.
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Seawater has a ph of 8.1. what is the concentration of oh–?
Which compound has the same empirical and molecular formula ethyne ethene ethane methane?
You have 40 g of a radioisotope. If the half-life of this radioisotope is 4 days, how many grams will remain after 12 days?
What is the result of mixing the two substances shown here together?
They are not attracted to each other because one is polar and one is nonpolar — is the correct answer
Which is an example of printing embedded in paper?
Question 7 options:
indented writing
trash marks
watermarks
spots
Indented writing and spots are the examples of printing embedded in paper.
What is printing?
Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The earliest known form of printing as applied to paper was woodblock printing, which appeared in China before 220 AD for cloth printing. However, it would not be applied to paper until the seventh century.
Later developments in printing technology include the movable type invented by Bi Sheng around 1040 AD and the printing press invented by Johannes Gutenberg in the 15th century. The technology of printing played a key role in the development of the Renaissance and the Scientific Revolution and laid the material basis for the modern knowledge-based economy and the spread of learning to the masses.
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3) The amount of energy it takes to eject an electron from the surface of a metal is 4.15 x 10-19J. If light with a wavelength of 625nm is shined on the metal, what will happen? Prove your answer mathematically by finding the frequency and energy of the wave.
15 POINTS
When calcium forms an ion, what is its charge?
2+
3+
2-
3-
Which is not true of radioactive half-life? radioactive half-life is increased by heating the isotope. independent of the physical or chemical form of the isotope. the time required for the level of radioactivity in a sample to be cut in half. independent of the amount of radioactive material present?
Answer:
"Radioactive half-life is increased by heating the isotope" is not true.
Explanation:
The radioactive half-life is the time required for half of any given amount of a substance (or isotope), to undergo radioactive decay.
This radioactive decay does not depend on the physical form of the substance nor it depends on the temperature.
Bromine dichloride, BrCl2, decomposes to form bromine and chlorine at equilibrium according to the following equation:
2BrCl2(g) + heat ⇌ Br2(g) + 2Cl2(g)
For the following change, how would the reaction shift (toward the products, reactants, or no change)?
The temperature is increased?
When the equilibrium of the decomposition of bromine dichloride is disturbed by increasing temperature, the reaction shifts towards the reactants according to Le Chatelier's principle.
If the temperature is increased for the decomposition of bromine dichloride, BrCl2, the reaction will shift towards the reactants. According to Le Chatelier's principle, if a chemical system at equilibrium experiences a change in concentration, temperature, volume, or pressure, then the equilibrium shifts to counteract the imposed change and re-establish equilibrium. In this endothermic reaction, heat is absorbed to convert BrCl2 into bromine, Br2, and chlorine, Cl2. Therefore, increasing the temperature adds heat to the system, which will shift the equilibrium towards the reactants (BrCl2) to absorb the excess heat.
Which of the following is not true regarding an acid?
a. can donate a proton (H+) to some other substance
b. can accept a proton (H+) from some other substance
c. releases hydrogen ions (H+)when dissolved in water
d. neutralizes hydroxide ions to form water
The standard Gibbs free energy of formation of ________ is zero. (
a. Rb(s) (
b. H2(
g. (
c. Pb(s)
The standard Gibbs free energy of formation for Rubidium solid (Rb(s)), Hydrogen gas (H2(g)), and Lead solid (Pb(s)), which are each in their standard state, is zero by definition.
Explanation:The standard Gibbs free energy of formation of any element in its most stable form is zero by definition. This means that for elements in their standard states, such as Rubidium solid (Rb(s)), Hydrogen gas (H2(g)), and Lead solid (Pb(s)), the standard Gibbs free energy of formation is zero.
Considering the standard state refers to the most stable form of an element at 1 atm pressure and 25°C, the correct answer to the question is that the standard Gibbs free energy of formation of all the listed elements, which are in their standard states, is zero.
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A group of chemistry students had to identify six white powders. The students used a variety of tests to identify the powders. They computed the density of each powder. They checked to see if any dissolved in water. One of the powders did not dissolve in water and they thought it was cornstarch. Someone knew that cornstarch felt slippery and reacted with iodine. The students put a few drops of iodine on each white powder. One powder turned black; they guessed that it was cornstarch. They heated the powders in a Bunsen burner flame to see if any would melt. One did and they guessed it might be a sugar. Which test result indicated a chemical change had taken place? A) dissolves in water B) feels slippery in water C) melts when heated in a flame D) turns black when iodine is added
Submarines sometimes make a "pinging" sound to determine the depth of an object in the ocean. This process is called
A. sonar.
B. radar.
C. refraction.
D. diffraction
Given the equation, c2h4(g + 3o2(g ? 2co2(g + 2h2o(l +1411 kj, how much heat is released when 8.00 g of o2 react?
Final answer:
To find the heat released when 8.00 g of O₂ react, convert grams to moles based on O₂'s molar mass. Then, use stoichiometry to determine that 117.58 kJ of heat is released for 0.25 moles of O₂ reacting.
Explanation:
The question is asking how much heat is released when 8.00 g of O₂ (oxygen) reacts according to the provided chemical equation. To solve this, we first need to identify the molar mass of oxygen and then determine how many moles of O₂ is present in 8.00 g. The molar mass of O₂ is about 32.00 g/mol, so 8.00 g of O₂ is 0.25 moles. The balanced equation given is for 3 moles of oxygen gas, so we need to use stoichiometry to find out how much heat will be released when 0.25 moles react.
From the given equation, for every 3 moles of O₂ that react, 1411 kJ of heat is released. We can set up a proportion to find the heat released when 0.25 moles react:
(1411 kJ / 3 moles O₂) x 0.25 moles O₂ = 117.58 kJ
Therefore, when 8.00 g of O₂ react, 117.58 kJ of heat is released.
What term refers to the coldest and densest zone, deep below the surface of a lake?
Answer: Hypolimnion
Explanation:
The hypolimnion layer is found in the dense region of lake. It is bottom layer of water in a thermally stratified lake.
This region has lowest oxygen concentration,and it lies below the thermocline.
It is the deepest and coldest layer found in lake. It has very less oxygen and maximum amount of sediments is also found there.
There reaches no light so photosynthesis id not possible there. The temperature there is almost 4 °C throughout the year.
Tritium (31h) is an isotope of hydrogen that is sometimes used to make the hands of watches glow in the dark. the half-life of tritium is 12.3 years. after 49 years, approximately how much of the original tritium remains?
Answer:
6.31%
Explanation:
In order to solve this, you need to use the expression to calculate half life, which is the following:
C = Co e^-t λ (1)
Where:
C: concentration after t has passed
Co: initial concentration
t: time that has passed
λ: lambda which relation half life time
λ this can be calculated with the following expression:
λ = ln2 / t(1/2) (2)
So, let's calculate λ first and then, the concentration. In this case, we will assume that we begin with a concentration at 100%.
The value of lambda is:
λ = ln2 / 12.3
λ = 0.0564
Now, let's use (1) to calculate the concentration after 49 years:
C = 100 e^ (-49 * 0.0564)
C = 100 e^(-2.7636)
C = 6.31 %
And this will be the tritium remaining after 49 years
Each astronaut produces 8.8 x 10^2 g CO2 per day that must be removed from the air on the shuttle. If a typical shuttle mission is 9 days, and the shuttle can carry 3.50 x 10^4 g LiOH, what is the maximum number of people the shuttle can carry for one mission
What is the molarity of a salt solution that is made from 31.0 grams of ca3(po4)2 placed in a volumetric flask and filled to the 2 liter line with distilled water?
"if the volume is kept constant, and nothing is added to the reaction mixture, what happens to the partial pressure of nitrogen during the course of the reaction?"
The partial pressure of nitrogen during the reaction if the volume is kept constant and nothing is added to the reaction mixture, then the pressure is decreases.
What is pressure ?Pressure is defined as the force applied perpendicular to an object's surface per unit area over which that force is distributed. Gauge pressure is the pressure in relation to the surrounding atmosphere. Pressure is expressed using a variety of units.
Measuring the pressure of a substance is an important part of the manufacturing process in many industries. Obtaining accurate and meaningful data is critical in determining product quality and consistency. For these reasons, precise sensors are critical in gathering this information.
A pascal is a pressure of one newton per square metre, or one kilogram per metre per second squared in SI base units. For many purposes, this unit is inconveniently small, and the kilopascal (kPa) of 1,000 newtons per square meter is more commonly used.
Thus, The partial pressure of nitrogen during the reaction if the volume is kept constant and nothing is added to the reaction mixture, then the pressure is decreases.
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a test done under standard conditions is referred to as what in chemistry? A. STP B. Control C. Rate Constant D. Kinetics E. None of the above
A chart that organizes elements by their chemical properties and increasing atomic number is the
When 14.0 g of zinc metal reacts with excess hcl, how many liters of h2 gas are produced at stp? when 14.0 g of zinc metal reacts with excess hcl, how many liters of h2 gas are produced at stp? 9.60 l 4.80 l 0.208 l 0.416 l?
The chemical reaction is given as:
[tex]Zn(s)+2HCl(aq)\rightarrow ZnCl_{2}(aq)+H_{2}(g)[/tex]
First, calculate the number of moles of zinc:
Number of moles = [tex]\frac{Given mass in g}{Molar mass}[/tex]
Given mass of zinc = [tex]14.0 g[/tex] and molar mass of zinc = [tex]65.4 g/mol[/tex]
Number of moles = [tex]\frac{14.0 g}{65.4 g/mol}[/tex]
= [tex]0.2140 moles[/tex]
Now, moles of hydrogen = [tex]number of moles of zinc\times \frac{1 mol of hydrogen}{1 mol of zinc}[/tex] ( as 1 mole of zinc gives 1 mole of hydrogen)
= [tex]0.2140\times \frac{1 mol of hydrogen}{1 mol of zinc}[/tex]
= [tex]0.2140 mol[/tex] of hydrogen.
Volume of hydrogen is calculated by:
[tex]PV=nRT[/tex]
where, P = pressure = 1 atm at STP
V = volume
n= number of moles
R = gas constant = [tex]0.082 Latm/Kmol[/tex]
T = temperature= 273 K at STP
Now, insert the values in formula, we get
[tex]V=\frac{nRT}{P}[/tex]
[tex]V=\frac{0.2140 mol\times 0.082 Latm/Kmol\times 273 K}{1 atm}[/tex]
[tex]V=\frac{0.2140 mol\times 0.082 Latm/Kmol\times 273 K}{1 atm}[/tex]
[tex]V=4.790 L\simeq 4.80 L[/tex]
Thus, volume of hydrogen is [tex]4.80 L[/tex] i.e. second option is the correct answer.
Do you feel that people’s safety is compromised when they live near a nuclear power plant? Why or why not? What sort of information do you think that someone living near a power plant should try to obtain? Why?
If the concentration of h uons were to decrease what would happen to the oh ions
A solution in which the hydroxide-ion concentration is 1x10^-2 is
Light striking a mirror at a 50° angle will be reflected at an angle _____.
Equal TO 50 degree because angle of incidence is equal to angle of reflection.
Answer:
equal to 50 degress
Explanation:
An aqueous solution of an unknown quantity of a nonelectrolyte solute is found to have a freezing point of −0.58°c.what is the molal concentration of the solution?
Final answer:
The molal concentration of the aqueous solution with a freezing point of -0.58°C is 0.312 mol/kg, calculated using the formula for freezing point depression and the molal freezing-point depression constant for water.
Explanation:
To determine the molal concentration of the solution based on the given freezing point depression, we use the formula ΔTf = Kf × m, where ΔTf is the change in freezing point, Kf is the molal freezing-point depression constant for water, and m is the molality of the solution.
For water, Kf is -1.86°C/m. The change in freezing point (ΔTf) can be calculated as the difference from water's normal freezing point, 0°C, to the solution's freezing point, which is -0.58°C. Thus, ΔTf = 0°C - (-0.58°C) = 0.58°C.
Plugging the values into the equation:
ΔTf = Kf × m
0.58°C = (-1.86°C/m) × m
m = 0.58°C / -1.86°C/m
m = 0.312 mol/kg
Therefore, the molal concentration of the solution is 0.312 mol/kg.
What volume of 0.45 M LiOH would be needed to neutralize 60.0 mL of 0.15 M Hi?
To neutralize 60.0 mL of 0.15 M HCl, 20.0 mL of 0.45 M LiOH is required. The neutralization reaction proceeds in a 1:1 molar ratio.
Explanation:To calculate the volume of 0.45 M LiOH required to neutralize 60.0 mL of 0.15 M HCl, we use the neutralization reaction where LiOH reacts with HCl in a 1:1 molar ratio:
LiOH + HCl → LiCl + H2OFirst, calculate the number of moles of HCl:
moles HCl = volume (L) × molarity (M) = 0.060 L × 0.15 M = 0.009 moles
Since the molar ratio is 1:1, 0.009 moles of LiOH will also be needed.
Then, calculate the volume of LiOH solution:
Volume LiOH = moles LiOH / molarity of LiOH = 0.009 moles / 0.45 M = 0.020 L or 20.0 mL
Therefore, 20.0 mL of 0.45 M LiOH is required to neutralize 60.0 mL of 0.15 M HCl.