Chemistry Answers

Write the correct name for each of the following structures.

A. CH3CH2CH = CHCH2CH2CH = CH2

B. CH3CH2C = CCH2CH3

if 500,000 kj of heat are released by the reaction, how grams of C12H26 must have been consumed

For the following overall cell reaction, write the oxidation and reduction half-reactions, calculate the standard cell potential, E^0cell and determine if the reaction is spontaneous or not. Show your work.

Fe^3+(aq) + Cu^+(aq) —> Fe^2+(aq) + Cu^2+(aq)

Use the IUPAC rules to name the following structures:

A. CH3

I

CH3CH2CH2CH2CHCH3

I

CH2

I

CH3

B. CH3

I

CH2CH2CH2CH2CH2CH2CH3

Draw the structure of each of the following alkanes.

A. 2,3,4 - trimethylpentane

B. 2 - methylheptane

Calculate the standard entropy values for the following reactions at 25°C.

1. N2(g) + 3H2(g) ⟶ 2NH3(g)

2. H2(g) + Cl2(g) ⟶ 2HCl(g)

3. 2CO2(g) + O2(g) ⟶ 2CO2(g)

4. 3O2(g) ⟶ 2O3(g)

5. 2NH3 (g) + CO2 (g) ⟶ NH2CONH2 (aq) H2O(l)

Question 23

25.00 cm³ of a 0.7892 mol.dm^-3 solution of potassium hydroxide is transferred to an empty 350.00 cm³ volumetric flask. This flask is made up to the mark with distilled water and then shaken well. The concentration of the potassium hydroxide in this second flask is:

a. 0.01109 mol.dm^-3

b. 0.05637 mol.dm^-3

c. 0.7892 mol.dm^-3

d. 17.74 mol.dm^-3

e. None of the above.

Question 24

What is the molarity of glacial acetic acid (CH₃COOH, Mr = 60.05 g/mol) at 25°C given that the density of acetic acid at that temperature is 1.049 g/mL?

a. 0.0174 M

b. 0.057 M

c. 57.2 M

d. 60.1 M

e. None of the above

 Question 25

Calculate the molarity of a KF (aq) solution containing 116.2 g of KF in 3.00 L of solution?

a. 0.02585 M

b. 0.667 M

c. 38.7 M

d. 58.1 M

e. None of the above

Question 19

Suppose that a solution is prepared by mixing 25 mL (0.22 mol, 16 g) of pentane (the solute) with 45 mL (0.34 mol, 30 g) of hexane (the solvent). If the volumes add on mixing, answer questions 19-21 below.

 Calculate the molality of the pentane

a. 3.1 mol/kg

b. 4.8 mol/kg

c. 7.3 mol/kg

d. 3.1 mol/L

e. 7.3 mol/L

Question 20

Calculate the molarity of the pentane?

a. 3.1 mol/kg

b. 7.3 mol/kg

c. 3.1 mol/L

d. 7.3 mol/L

e. 45.8 mol/L

Question 21

What is the mole fraction of the pentane?

a. 0.35

b. 0.39

c. 0.64

d. 39%

e. 64 %

 Question 22

If I prepare a solution by adding 25 mL of 2.0 M NaOH into a 500 mL volumetric flask, and filling the flask to the mark with water, what will the final concentration of the solution be?

a. 0.05 M

b. 0.10 M

c. 0.5 M

d. 2.0 M

e. 40.0 M

Question 14

In the above reaction in question 13, 2 moles of Mg and 5 moles of O₂ are allowed to react.

Which reagent is the limiting reagent?

a. Mg

b. O₂

c. MgO

d. There is no limiting reagent

e. Both Mg and O₂ are limiting reagents

Question 15

What is the maximum number of moles of MgO that can be formed?

a. 1 mol

b. 2 mol

c. 5 mol

d. 40.3 mol

e. 80.6 mol

Question 16

Calculate how many moles of the excess reagent remain unreacted.

a. 1 mol

b. 2 mol

c. 4 mol

d. 5 mol

e. No excess reagent remains unreacted

Question 17

Suppose that the actual moles of MgO produced was 0.5 mol, what is the percentage yield of MgO?

a. 0.62%

b. 1.2%

c. 10%

d. 25%

e. 50%

Question 18

The value of a solution concentration unit that may change with temperature is

a. molarity.

b. mole fraction.

c. molality.

d. mole percentage.

e. weight percentage.

Question 9

Calculate the number of moles of NH₃ present in 100 g of NH₃

a. 0.170 mol

b. 5.87 mol

c. 17.0 mol

d. 100 mol

e. 1703 mol

Question 10

Calculate the mass percentage of hydrogen in methane, CH₄

a. 0.062 %

b. 0.251 %

c. 6.28 %

d. 12.6 %

e. 25.1 %

 Question 11

A compound which contains 0.0130 mol C, 0.390 mol H and 0.065 mol O. What is the empirical formula for this compound?

a. CHO

b. CH₅O₂

c. CH₃₀O₅

d. CH₃₉O₆

e. C₂H₆₀O₁₀

Question 12

What is the empirical formula for a compound that contains 17.34 % hydrogen and 82.66 % carbon by mass?

a. CH

b. CH₂

c. CH₃

d. C₂H₅

e. C₅H

 Question 13

Consider the following information to answer questions 13-17 below:

The unbalanced reaction of magnesium with oxygen is:

Mg + O₂ → MgO

 The correct balanced reaction is:

a. Mg₂ + O₂ → 2MgO

b. 2Mg + ½ O₂ → Mg₂O

c. 2Mg + O₂ → 2MgO  

d. Mg + O₂ → MgO₂

e. None of the above