The half-life of an isotope that decays to 6.25% of its original activity in 18.9 hours is 4.725 hours. This is calculated by understanding that the isotope undergoes 4 half-lives to reach the 6.25% activity.
Explanation:The half-life (T1/2) of a radioactive isotope refers to the time period for half of the original nuclei to decay. In this case, the isotope decays to 6.25% of its original activity in 18.9 hours which means it goes through 4 half-lives (since (1/2)^4 = 1/16 which approximately equals 6.25%). Hence, the half-life of this isotope is 18.9/4 = 4.725 hours.
This concept is derived from the exponential decay of unstable radioisotopes where half-life (T1/2) is calculated by dividing the total time by number of half-lives.
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The smallest piece of a compound that retains characteristics of a compound is
Classify these molecules as polar or nonpolar bcl3
Boron trichloride ([tex]BCl_3[/tex]) is a nonpolar molecule due to its symmetrical structure and equal electron-sharing among the boron and chlorine atoms.
Explanation:The molecule [tex]BCl_3[/tex], known as boron trichloride, is classified as nonpolar. This classification is due to its symmetrical, trigonal planar molecular structure and that there are no lone pairs of electrons on boron. The electron density regions in[tex]BCl_3[/tex] are evenly distributed which gives rise to equal sharing of electrons among the boron and chlorine atoms. With the 120° angles between the B-Cl bonds, any partial charges formed along these polar bonds are cancelled out, making the molecule nonpolar in nature.
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BCl₃ is a nonpolar molecule due to its trigonal planar shape, which causes the dipole moments of the polar B-Cl bonds to cancel out.
To determine if the molecule BCl₃ is polar or nonpolar, we need to examine the molecular geometry and the distribution of charges. BCl₃, or boron trichloride, has a trigonal planar shape according to VSEPR theory. This shape means the three chlorine atoms are symmetrically arranged around the central boron atom at 120° angles.
Although each B-Cl bond is polar due to the difference in electronegativity between boron and chlorine, the symmetric arrangement leads to the dipole moments canceling each other out. As a result, BCl₃ is a nonpolar molecule because it has no net dipole moment.
In summary:
The geometry of BCl₃ is trigonal planar.Each B-Cl bond is polar.The symmetry causes the dipole moments to cancel out.Therefore, BCl₃ is classified as a nonpolar molecule.
20)
Marie is constructing a circuit board and observes that her current increases as she adds resistors. What statement explains why the current increases?
A) She is constructing a series circuit board so adding resistors draws more current.
B) She is constructing a parallel circuit and adding resistors increases the voltage.
C) She is constructing a series circuit so increasing the resistance also increases voltage and current.
D) She is constructing a parallel circuit board and the added resistors create more paths for the current, decreasing total resistance.
It's actually D.
She is constructing a parallel circuit board and the added resistors create more paths for the current, decreasing total resistance.As more resistors are added to a parallel circuit the number of paths for the current increases, allowing electrons to flow more freely and increasing the current.
Which of the following is a natural cause of wildfires
Answer:
lightning
Explanation:
Natural fires are generally started by lightning, with a very small percentage started by spontaneous combustion of dry fuel such as sawdust and leaves. On the other hand, human-caused fires can be due to any number of reasons. Some classifications include smoking, recreation, equipment, and miscellaneous.
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Which of the following tools could have become cross-contaminated during the experiment if you had not cleaned them carefully between successive tests?
A. Spoon
B. Beaker
C. Stirring Rod
D. Graduated Cylinder
E. Distilled water in a spray bottle
Explanation:
When we are using spoon, beaker, stirring rod and graduated cylinder then they directly come in contact with the chemical we are using. Hence, if they are not washed thoroughly then chemicals remain deposited over them.
As a result, when successive test are performed using the same contaminated apparatuses then we do not get the desired results.
Whereas distilled water in a spray bottle if poured without touching or coming in contact with any kind of chemicals.
Hence, we can conclude that spoon, beaker, stirring rod and graduated cylinder are the tools that could have become cross-contaminated during the experiment if you had not cleaned them carefully between successive tests.
Answer:
A. Spoon, B. Beaker, C. Stirring Rod, D. Graduated Cylinder
Explanation:
If 72.0 grams of aluminum are reacted with 252 grams of hydrochloric acid, how many grams of aluminum chloride are produced by this reaction? 2al(s) + 6hcl(aq) → 2alcl3(aq) + 3h2(g)
Final answer:
To determine the grams of aluminum chloride produced in the reaction, use the given balanced chemical equation and the molar masses of aluminum and aluminum chloride. Convert the given masses of aluminum and hydrochloric acid to moles and use the stoichiometric ratios to determine the moles of aluminum chloride produced. Finally, convert the moles of aluminum chloride to grams.
Explanation:
To determine the grams of aluminum chloride produced in the reaction, we need to use the given balanced chemical equation and the molar masses of aluminum (Al) and aluminum chloride (AlCl3). The molar mass of Al is approximately 26.98 g/mol, while the molar mass of AlCl3 is approximately 133.34 g/mol.
First, we convert the given masses of aluminum (72.0 g) and hydrochloric acid (252 g) to moles using their respective molar masses. Using the ratios from the balanced chemical equation, we can then determine the moles of aluminum chloride produced.
Starting with 72.0 g of Al:
72.0 g Al * (1 mol Al / 26.98 g Al) * (2 mol AlCl3 / 2 mol Al) * (133.34 g AlCl3 / 1 mol AlCl3) = 398.908 g AlCl3
Therefore, approximately 398.908 grams of aluminum chloride are produced.
Identify the brønsted base in the forward reaction hpo2− 4 (aq) + hno3(aq) ⇀↽ no− 3 (aq) + h2po− 4 (aq). 1. h2po− 4 (aq) 2. hno3 3. hpo2− 4 4. no− 3
The Brønsted base in the forward reaction HPO4²-(aq) + HNO3(aq) ⇀↽ NO3¯ (aq) + H2PO4¯ (aq) is HPO4²-(aq) because it accepts a proton in this reaction.
Explanation:To identify the Brønsted base in the reaction HPO4²-(aq) + HNO3(aq) ⇀↽ NO3¯(aq) + H2PO4¯(aq), let's recognize the definitions of a Brønsted-Lowry base and acid.
A Brønsted base is a proton (H+) acceptor, whereas a Brønsted acid is a proton donor. In the forward reaction, HNO3 donates a proton; making it the Brønsted acid. The species that accepts the proton is HPO4²-. Therefore, HPO4²- is the Brønsted base in the forward reaction of this equilibrium.
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In the reaction, HPO₄²⁻ is the Brønsted base as it accepts a proton from HNO₃. HNO₃ acts as the Brønsted acid. Therefore, option 3: HPO₄²⁻ is correct.
In the forward reaction HPO₄²⁻ (aq) + HNO₃ (aq) ⇄ NO₃⁻ (aq) + H₂PO₄⁻ (aq), we need to identify the Brønsted base.
A Brønsted base is defined as a substance that can accept a proton (H⁺). In this reaction:
HPO₄²⁻ is acting as a Brønsted base because it accepts a proton from HNO₃ to form H₂PO₄⁻. HNO₃ acts as a Brønsted acid since it donates a proton.So, the correct answer is option 3: HPO₄²⁻.
Complete Question.
Identify the Brønsted base in the forward reaction HPO₄²⁻ (aq) + HNO₃(aq) ⇄ NO₃⁻ (aq) + H₂P0₄⁻ (aq).
1. NO₃⁻
2. H₂PO₄⁻ (aq)
3. HPO₄²⁻
4. HNO₃
How many moles of ions are produced by the dissociation of 1 mol of al2(co3)3?
The moles of ions produced are 5.
What are moles?The mole is a SI unit of measurement that is used to calculate the quantity of any substance.
Aluminum Carbonate on Dissociates into Aluminum Ions and carbonate Ions
[tex]Al_2(CO_3)_3 = 2 Al6+^3 + 3 CO_3^-^2[/tex]
On dissociation [tex]Al_2(CO_3)_3[/tex] produces five Ions in total.
Al⁺² = 2
CO₃⁻² = 3
Thus, The moles of ions produced are 5.
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Complete combustion of glucose (c6h12o6). oxygen gas is the other reactant in this combustion reaction. the products are co2 and h2o
The direction of the magnetic field produced by an electric current will change when the direction of the ____ changes
To find the number of protons, neutrons, and electrons in a particular atom, you must know the mass number and the atomic number of the atom
Define what electronegativity is and explain the pattern on the table as you move to the right across it.
Silver nitrate (AgNO3) reacts with hydrochloric acid (HCl) to produce nitric acid (HNO3) and silver chloride (AgCl). AgNO3 + HCl HNO3 + AgCl Which of the following actions would increase the reaction rate? A. increasing the concentration of HCl B. decreasing the concentration of AgCl C. decreasing the concentration of AgNO3 D. increasing the concentration of HNO3
Silver nitrate (AgNO₃) reacts with hydrochloric acid (HCl) to produce nitric acid (HNO₃) and silver chloride (AgCl). Increasing the concentration of HCl would increase the rate of reaction and the correct option is option A.
The rate of reaction or reaction rate is the speed at which reactants are converted into products. It is the measure of the change in concentration of the reactants or the change in concentration of the products per unit time. If a reaction has a low rate, that means the molecules combine at a slower speed than a reaction with a high rate.
Factors influencing the rate of reaction are:
1. surface area of a solid reactant
2. concentration and pressure of a reactant
3. temperature
4. nature of reactants
5. presence/absence of a catalyst
Thus, the ideal selection is option A.
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Which of the space missions involved the deployment of lunar rover
A. Voyager 1
B. Gemini
C. Mercury
D. Apollo
Please help asap on clock
Answer:
The answer is D.Apollo
Explanation:
The statement that describes the space missions involved the deployment of lunar rover is "Apollo."
What is a space mission?
A space mission is defined as the act of sending a space item to its designated location and then performing scientific or technological operations there. An examination of the reaches of the universe beyond Earth's atmosphere using crewed and uncrewed spacecraft, with the goal of increasing understanding of the cosmos and benefiting humanity.
The majority of the deployment occurred automatically as the rover was released from the bay.
The lunar rovers of Apollo 15, 16, and 17 anchored American automotive culture on the moon's surface while broadening the scientific scope of the missions' astronaut explorers.
Hence the correct option is Apollo.
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The solubilty of a gas is 1.6 g/l at 760 mmhg what is the solubility of the same gas at a pressure of 2.5 atm? assume temperature to be constant
Question 4 if 0.587 g of nickel metal reacts with 1.065 g of chlorine gas, what is the empirical formula of the nickel chloride product? ni2cl3 ni3cl2 nicl3 nicl nicl2
The empirical formula of nickel chloride, given the masses of nickel and chlorine, is c) NiCl₃
Determining the Empirical Formula of Nickel Chloride
To determine the empirical formula of nickel chloride from the given masses of nickel (0.587 g) and chlorine (1.065 g), follow these steps:
Convert the mass of each element to moles:
Nickel (Ni): 0.587 g ÷ 58.69 g/mol = 0.0100 mol
Chlorine (Cl): 1.065 g ÷ 35.45 g/mol = 0.0300 mol
Determine the simplest whole number ratio:
Nickel: 0.0100 mol ÷ 0.0100 mol = 1
Chlorine: 0.0300 mol ÷ 0.0100 mol = 3
Write the empirical formula: Hence, the simplest ratio of Nickel to Chlorine is 1:3, making the empirical formula NiCl₃
How many core electrons are in a ground state atom of selenium?
Selenium has a total of 28 core electrons. This is because the electrons that fill the inner atomic orbitals of an atom, which totals 28 in the case of Selenium, are referred to as the core electrons.
Explanation:The ground state atom of Selenium (Se) has an atomic number of 34. This means it has 34 electrons in total. Electrons in atoms are distributed in energy levels or shells, with each able to accommodate a certain number of electrons. The electrons in the outermost shell, known as valence electrons, are responsible for chemical reactivity, whereas those filling the inner shells are called core electrons. Selenium's electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴. The first 28 electrons (1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰) fill the core atomic orbitals, so Selenium has 28 core electrons in its ground state.
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a 4 kilogram cat is resting on top of a bookshelf that is 3 meters high what is the cats gravitational potential energy relative to the floor if the acceleration due to gravity is 9.8m/s A.7j B. 29j C.12j D.118j
3L of nitrogen gas is heated from 20°C to 80°C. What is the new volume of the gas, if pressure remains constant?
Isomers have identical _________formulas; however, they have different ___________formulas.
Empirical
Molecular
Structural
Answer:
Isomers have identical Molecular formulas; however, they have different Structural formulas.
Explanation:
Hello,
In this case, it is widely known that isomers have identical molecular formulas and different structural formulas as shown for the compound having the following molecular formula:
[tex]C_2H_6O[/tex]
In such a way, two feasible compounds could have the aforesaid molecular formula, which are dimethyl ether and ethanol respectively as shown below:
[tex]CH_3-O-CH_3\\CH_3-CH_2-OH[/tex]
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How many moles of oxygen atoms do 1.5 moles of co2 contain?
Final answer:
1.5 moles of carbon dioxide (CO2) contain 3 moles of oxygen atoms because each CO2 molecule is composed of two oxygen atoms.
Explanation:
The question 'How many moles of oxygen atoms do 1.5 moles of CO2 contain?' involves understanding the composition of a carbon dioxide (CO2) molecule.
Each molecule of CO2 consists of one carbon atom and two oxygen atoms. Therefore, for every mole of CO2, there are two moles of oxygen atoms. To find the number of moles of oxygen atoms in 1.5 moles of CO2, we simply need to multiply 1.5 moles by 2 (the number of oxygen atoms per mole of CO2).
1.5 moles CO2 x 2 moles O per mole CO2 = 3 moles O
Thus, 1.5 moles of CO2 contain 3 moles of oxygen atoms.
How many grams of magnesium chloride are needed to make 700ml of a 1.4 m solution?
Indentify two advantages in daylight saving time
Use the periodic table to answer the questions: Which is the correct electron configuration for sodium (Na)?
1s22s22p62d1
1s22s22p63s1
1s22p63d3
Answer: The correct answer is [tex]1s^22s^22p^63s^1[/tex]
Explanation:
Electronic configuration is defined as the configuration in which total number of electrons are represented which are present in an element.
Number of electrons are determined by the atomic number of that element.
Atomic number of Sodium = 11
Electronic configuration of sodium element (Na) : [tex]1s^22s^22p^63s^1[/tex]
Hence, the correct answer is [tex]1s^22s^22p^63s^1[/tex]
What about uranium room temperature is it "SOLID LIQUID or GAS)?
Ch3cooh (acetic acid) can form hydrogen bonds between its molecules. based on the lewis structure shown below, how many hydrogen bond donor and acceptor atoms does this molecule have?
Acetic acid has one hydrogen bond donor atom and two hydrogen bond acceptor atoms, found in its -COOH group.
Explanation:Acetic acid CH3COOH, is capable of forming hydrogen bonds due to the presence of a hydrogen atom bonded to an oxygen atom in its -COOH group. This group has one hydrogen atom that can act as a hydrogen bond donor (attached to oxygen by a polar bond). Furthermore, it has two lone pairs of electrons on the oxygen which can each accept a hydrogen bond, thus making it a hydrogen bond acceptor. Therefore, acetic acid has one hydrogen bond donor atom and two hydrogen bond acceptor atoms.
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Name three factors that influence the rate at which a solute dissolves in a solvent.
Recall that your hypothesis is that these values are the fraction of atoms that are still radioactive after n half-life cycles. Record in the appropriate blanks.
Answer : A= 0.5, B = 0.25 , C = 0.125, D = 0.015625 and E = 0.00390625
Explanation :
Half life of a substance is defined as the amount of time taken by the substance to reduce to half of its original amount.
Here n represents the number of half lives.
The amount of substance that remains after n half lives can be calculated using the given formula, [tex] 0.5^{n} [/tex]
So when we have n =1,
Fraction of substance that remains = 0.5¹ = 0.5.
That means after first half life over, the amount of substance that remains is 0.5 times that of original.
Therefore we have A = 0.5
When n = 2, we have 0.5² = 0.25
So when 2 half lives are over, the amount of substance that remains is 0.25 times that of original
Therefore B = 0.25
When n = 3, we have 0.5³ = 0.125
So when 3 half lives are over, the amount of substance that remains is 0.125 times that of original.
Therefore we have C = 0.125
When n = 6 , we have 0.5⁶ = 0.015625
So D = 0.015625
When n = 8, we have 0.5⁸ = 0.00390625
Therefore E = 0.00390625
The values for A, B, C, D and E are 0.5, 0.25, 0.125, 0.015625 and 0.00390625 respectively.
15 POINTS
When calcium forms an ion, what is its charge?
2+
3+
2-
3-
The answer is:
A) 2+
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What explains the change in ionization energy that occurs between removing the first and second electrons from an atom
Answer:
B. The ionization energy increases because the ratio of the protons to electrons increases.
Explanation:
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