On a mission to a newly discovered planet, an astronaut finds copper abundances of 69.97 % for 63Cu and 31.03 % for 65Cu. What is the atomic mass of copper for this location? The mass of 63Cu is 62.9300 amu . The mass of 65Cu is 64.9200 amu . Express your answer to two decimal places, and include the appropriate units.

Answers

Answer 1

Answer: Okay so to find the average atomic mass of copper in this location, you want to take the percentage of abundance of an isotope and multiply (in decimal form) that by it's atomic mass, then you would add that with the product of the % of abundance of the other isotope times it's atomic mass.

(Side Note: Isotopes are atoms of the element that have the SAME number of protons but different number of neutrons, so they have different mass numbers. Also average atomic mass is the average of all the isotopes in an element - this number is the one that is shown on the periodic table of elements, not mass number).

Let me show you how to do this..

For the isoptope 63Cu I will first need to convert it's percentage of abundance into a decimal, because we don't use the percentage to multiply. 69.97% -> 0.6997. Now I am going to take it's atomic mass 62.9300 and multiply that by 0.6997.

62.9300*0.6997=44.0321

Now we still need to find calculate this for the isotope 65Cu. To convert 31.03% to a decimal I will just move the decimal point two places to the left, to get 0.3103.
So I am going to take this and multiply it by 64.9200 the atomic mass of the isotope 65Cu.

64.9200*0.3103=20.1447

Add the two of these to get the average atomic mass..
20.1447 + 44.0321=64.1768

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You have to prepare some 2 M solutions, with 10 g of solute in each. What volume of solution will you prepare, for each solute below? (Ar:H51,Li57,N514,O516,Mg524,S532.)a lithium sulfate, Li2SO4

Answers

Answer:

0.045 L or 45 mL

Explanation:

Moles = Mass/M.Mass

Moles = 10 g / 109.94 g/mol

Moles = 0.09 moles

Also,

Molarity = Moles / Vol in L

Or,

Vol in L = Moles / Molarity

Vol in L = 0.09 mol / 2 mol/L

Vol in L = 0.045 L

Which laboratory test result can be used to determine if KCl(s) is an electrolyte?(1) pH of KCl(aq)
(2) pH of KCl(s)
(3) electrical conductivity of KCl(aq)
(4) electrical conductivity of KCl(s)

Answers

Answer: (3) electrical conductivity of KCl (aq)

Explanation: pH is the measure of acidity or alkalinity.

Conductance is the ability of a substance to be able to conduct electric current through it. Electrolyte is a solution which enables electric current to pass through them due to the presence of ions.

Ionic compounds do not conduct electricity in solid state as the ions are strongly held by strong coloumbic forces but in aqueous solutions they dissociate into ions and thus act as good conductors.

$KCl(aq)\rightarrow K^+(aq)+Cl^-(aq)$

The answer is (3) electrical conductivity of KCl(aq). The definition of electrolyte is that the substance that will ionize when dissolving in suitable ionizing solvent like water.

After creating a Beer's Law plot using standard solutions of Q, you determined the slope of Beer's Law to be 0.543 M-1. Your unknown solution of Q tested in Part B of the experiment had an absorbance of 0.144. Determine the concentration (in molarity) of the unknown solution Q from Part B. Do not use scientific notation or units in your response. If Carmen adds zeros after the decimal place, your answer will still be graded correctly.

Answers

Answer : The concentration (in molarity) of the unknown solution Q is, 0.265

Explanation :

Using Beer-Lambert's law :

$A=\epsilon * C* l$

where,

A = absorbance of solution

C = concentration of solution

l = path length

$\epsilon$ = molar absorptivity coefficient

From the Beer's Law plot between absorbance and concentration we concldue that the slope is equal to $\epsilon * l$ and path length is 1 cm.

As we are given that:

Slope = 0.543 M⁻¹

and,

Slope = $\epsilon * l$

$\epsilon * l=0.543M^(-1)$

$\epsilon * 1cm=0.543M^(-1)$

$\epsilon=0.543M^(-1)cm^(-1)$

Now we have to determine the concentration (in molarity) of the unknown solution Q.

Using Beer-Lambert's law :

$A=\epsilon * C* l$

$0.144=0.543M^(-1)cm^(-1)* C* 1cm$

$C=0.265M$

Therefore, the concentration (in molarity) of the unknown solution Q is, 0.265

If'substance X is a liquid, substance Y is a gas, and substance Z is a solid, and all are at thesame temperature and pressure, then the order of increasing strength of their intermolecular
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Answers

The answer is Y < X < Z

Which of the following nonmetals forms a gas commonly found in our atmosphere? Rn,Cl,I,or N

Answers

N, our atmosphere is about 80% nitrogen(N) and about 20% oxygen(O)

Nitrogen (N) our atmosphere is 80% N

An element X has two isotopes. X–15 has 7 protons and 8 neutrons. Determine the atomic number and mass number of the second isotope, which has 10 neutrons in its nucleus. a. atomic number = 8; mass number = 9
b. atomic number = 8; mass number = 17
c. atomic number = 7; mass number = 17
d. atomic number = 7; mass number = 15

Answers

c. Atomic number = 7; mass number = 17

The atomic number of the first isotope is 7.

Isotopes of the same element have the same atomic number, so the atomic number of the second isotope must also be 7.

Mass number = no. of protons + no. of neutrons, or

A = p + n

∴ A = 7 + 10 = 17

Options “a.” and “b.” have the wrong atomic numbers, and option “d.” has the wrong mass number.

Answer:

Explanation:

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