Question 1

Which of the following statements about oxidation numbers is CORRECT?

Accepted Answer

The oxidation number of a monatomic ion is equal to its charge.

Question 2

Assign the oxidation number to chlorine in the hypochlorite ion, $$\mathrm{ClO^-}.$$

Accepted Answer

$$+1$$

Question 3

Which of the following best describes the role of an oxidizing agent in a redox reaction?

Accepted Answer

It accepts electrons and is reduced.

Question 4

Consider the reaction: $$\mathrm{Zn(s) + 2HCl(aq) \rightarrow $$ZnCl_2$$(aq) + H_2$(g)}. $$Using the activity series, which statement is correct?

Accepted Answer

Zinc is above hydrogen in the activity series and will displace hydrogen.

Question 5

A 1.0 g sample of Fe(s) and a 1.0 g sample of H$$_2O(l) $$both absorb 10.0 J of heat. Which sample experiences the greatest temperature change? (Specific heat of Fe = $$0.45\ \mathrm{J/g\cdot K}$$, H$$_2O$$ = $$4.18\ \mathrm{J/g\cdot K})$$

Accepted Answer

The Fe sample, because it has a lower specific heat.

Question 6

Calculate the heat required to raise the temperature of $$4.00\ \mathrm{g} of $$water by $$8.00\ ^\circ\mathrm{C}. ($$Specific heat of water = $$4.18\ \mathrm{J/g\cdot ^\circ C})$$

Accepted Answer

$$133\ \mathrm{J}$$

Question 7

Which of the following is TRUE about state functions?

Accepted Answer

State functions depend only on the initial and final states, not the path taken.

Question 8

A chemical reaction in a flask causes the temperature of the flask to decrease. Which of the following is TRUE?

Accepted Answer

The reaction is endothermic and absorbs heat from the surroundings.

Question 9

Given the reaction $$\mathrm{CH_4$(g) + 2O_2(g) \rightarrow CO_2$(g) + 2H_2O(l)}$$ with $$\Delta H = -890\ \mathrm{kJ/mol}$$, what does the negative sign indicate?

Accepted Answer

The reaction is exothermic and releases heat.

Question 10

Which of the following is the correct formula for calculating the heat absorbed or released by a substance?

Accepted Answer

$$q = mC\Delta T$$

Question 11

A system absorbs $$12.4\ \mathrm{J} of $$heat and does $$-4.2\ \mathrm{J} of $$work on the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = +8.2\ \mathrm{J}$$

Question 12

Which of the following statements about enthalpy ($$\Delta H) is $$FALSE?

Accepted Answer

$$\Delta H$$ depends on the path taken between reactants and products.

Question 13

Which process is exothermic?

Accepted Answer

Condensation of water vapor to liquid water.

Question 14

What is the standard enthalpy of formation ($$\Delta H_f^\circ) of an $$element in its most stable form at $$25^\circC $$and $$1$$ atm?

Accepted Answer

$$0\ \mathrm{kJ/mol}$$

Question 15

Which of the following reactions represents the standard enthalpy of formation of HCl(g)?

Accepted Answer

$$\frac{1}{2}\mathrm{H_2$(g)} + \frac{1}{2}\mathrm{Cl_2$(g)} \rightarrow \mathrm{HCl(g)}$$

Question 16

Using Hess's Law, what is the enthalpy change for the sublimation of 1 mole of ice, given the following data? 
$$\mathrm{H_2O(s) \rightarrow H_2O(l)}\ \Delta H = +6.01\ \mathrm{kJ/mol}$$
$$\mathrm{H_2O(l) \rightarrow H_2O(g)}\ \Delta H = +44.0\ \mathrm{kJ/mol}$$

Accepted Answer

$$+50.0\ \mathrm{kJ/mol}$$

Question 17

Which of the following best describes the use of bond enthalpies in calculating $$\Delta H$$ for a reaction?

Accepted Answer

$$\Delta H = \sum 	ext{Bond enthalpies of bonds broken} - \sum 	ext{Bond enthalpies of bonds formed}$$

Question 18

Estimate the enthalpy change for the reaction $$\mathrm{H_2$(g) + Cl_2$(g) \rightarrow 2HCl(g)}$$ using the following bond enthalpies: $$\mathrm{H-H} = 436\ \mathrm{kJ/mol}$$, $$\mathrm{Cl-Cl} = 243\ \mathrm{kJ/mol}$$, $$\mathrm{H-Cl} = 431\ \mathrm{kJ/mol}.$$

Accepted Answer

$$-249\ \mathrm{kJ}$$

Redox Reactions, Oxidation Numbers, Metal Activity Series, and Thermochemistry

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