Q: A 2.49 g sample of aniline ($$\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2$$, molar mass = 93.13 g/mol) is combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/$$^\circC. $$The temperature rises from 29.5$$^\circC to 69.8$^\circC. $$What is the standard enthalpy of combustion ($$\Delta H_{comb}^\circ) $$for aniline, in kJ/mol?

$$-3.20 \times 10^3$\ \mathrm{kJ/mol}$$

Q: A 14.3 mL sample of 0.140 M sucrose solution is prepared. How many molecules of sucrose are present?

$$1.21 \times 10$$^{21}$$ molecules

Question 1

Which of the following statements correctly describes the sign conventions for heat ($$q) $$and work ($$w) $$for a system that absorbs heat from the surroundings and does work on the surroundings?

Accepted Answer

$$q = +$$, $$w = -$$

Question 2

Which of the following processes is endothermic?

Accepted Answer

The vaporization of ethanol

Question 3

Which of the following is a strong electrolyte when dissolved in water?

Accepted Answer

KNO$$_3$$

Question 4

A student mixes 5.00 mL of 0.100 M KBr with 2.00 mL of 0.200 M MgBr$$_2. $$What is the final molarity of Br$$^-$$ ions in the mixture? (Assume volumes are additive.)

Accepted Answer

$$0.186\ \mathrm{M}$$

Question 5

Which of the following reactions represents the standard enthalpy of formation ($$\Delta H_f^\circ) $$for LiHSO$$_4(s$$)?

Accepted Answer

$$\mathrm{Li}(s) + \frac{1}{2}\ \mathrm{H}_2(g) + \mathrm{S}(s) + 2\ \mathrm{O}_2(g) \rightarrow \mathrm{LiHSO}_4(s)$$

Question 6

A 2.49 g sample of aniline ($$\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2$$, molar mass = 93.13 g/mol) is combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/$$^\circC. $$The temperature rises from 29.5$$^\circC to 69.8$^\circC. $$What is the standard enthalpy of combustion ($$\Delta H_{comb}^\circ) $$for aniline, in kJ/mol?

Accepted Answer

$$-3.20 	imes 10^3$\ \mathrm{kJ/mol}$$

Question 7

Which metal will reach the highest temperature if 100 J of heat is added to 25.0 g of each, all starting at the same temperature? (Specific heats: Zn = 0.387 J/g$$^\circC$$, Mg = 1.02 J/g$$^\circC$$, Fe = 0.450 J/g$$^\circC$$, Ag = 0.237 J/g$$^\circC$$, Pb = 0.127 J/g$$^\circC)$$

Accepted Answer

Lead

Question 8

A 376 g gold nugget at 288 K loses 4.85 kJ of heat to a snowbank. The specific heat of gold is 0.128 J/g$$^\circC. $$What is the final temperature of the nugget?

Accepted Answer

$$187\ \mathrm{K}$$

Question 9

How many lithium ions are present in 45.0 mL of 0.400 M Li$$_2CO$_3$$ solution?

Accepted Answer

$$2.17 	imes 10$$^{22}$$ ions

Question 10

A solution is made by diluting 70.0 mL of 0.274 M sodium sulfide to a total volume of 400 mL. What is the final concentration of sodium ions?

Accepted Answer

$$0.0959\ \mathrm{M}$$

Question 11

Calculate the heat released when 100.0 g of octane ($$\mathrm{C}_8\mathrm{H}_{18}$$, molar mass = 114.33 g/mol) undergoes complete combustion according to the reaction: $$2\ \mathrm{C}_8\mathrm{H}_{18} + 25\ \mathrm{O}_2 \rightarrow 16\ \mathrm{CO}_2 + 18\ \mathrm{H}_2\mathrm{O}$$, $$\Delta H_{rxn} = -11018\ \mathrm{kJ}.$$

Accepted Answer

$$4819\ \mathrm{kJ}$$

Question 12

A 2.49 g sample of aniline ($$\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2) is $$combusted in a bomb calorimeter. The temperature rises by 40.3$$^\circC $$and the calorimeter has a heat capacity of 4.25 kJ/$$^\circC. $$What is the total heat released by the sample?

Accepted Answer

$$171\ \mathrm{kJ}$$

Question 13

A student determines the percent of CuCO$$_3 in a $$mixture to be 65.45%. The actual value is 64.65%. What is the percent error, reported to the correct number of significant figures?

Accepted Answer

$$1.2\%$$

Question 14

The titration of 80.0 mL of an unknown concentration H$$_3PO$_4$$ solution requires 126 mL of 0.218 M KOH solution for complete neutralization. What is the concentration of the H$$_3PO$_4$$ solution?

Accepted Answer

$$0.114\ \mathrm{M}$$

Question 15

When 260 mL of $$1.50 	imes 10$$^{-4}$$ M HBr is added to 135 mL of 1.60$$ 	imes $$10^{-4} M Mg(OH$$)$$_2$$, the resulting solution will be:

Accepted Answer

Acidic

Question 16

A 14.3 mL sample of 0.140 M sucrose solution is prepared. How many molecules of sucrose are present?

Accepted Answer

$$1.21 	imes 10$$^{21}$$ molecules

Question 17

What mass of PbI$$_2 is $$precipitated when 35.5 mL of 2.00 M HI reacts with excess Pb(C$$_2H$_3O$_2$$)$$_2$$ and the percent yield is 94.0%? (Balanced equation: $$2\ \mathrm{HI} + \mathrm{Pb(C_2H_3O_2)_2} \rightarrow \mathrm{$$PbI_2$$} + 2\ \mathrm{HC_2H_3O_2})$$

Accepted Answer

$$16.4\ \mathrm{g}$$

Question 18

Which of the following best describes an endothermic reaction?

Accepted Answer

A positive $$\Delta H$$, absorbs heat from the surroundings, and feels cold to the touch.

General Chemistry 1A Exam 2 – Step-by-Step Study Guidance

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