Part II. Multiple choice, continued (3 points each). Name:__________________ Please circle your answer. There is only one correct answer to each question. 22. ∆E for a system that releases 12.4 J of heat and does 4.2 J of work on the surroundings is ____________ J. A) 16.6 B) 12.4 C) –8.2 D) –16.6 23. ∆H for an endothermic process is _________ while ∆H for an exothermic process is __________. A) zero, positive B) positive, negative C) negative, zero D) negative, positive 24. The value of ∆H˚ for the reaction below is –283 kJ. Calculate the heat (kJ) released to the surroundings when 12.0 g of CO reacts completely. CO (g) + O2 (g) à CO2 (g) A) 121 B) 660 C) 283 D) 212 25. Given the following reactions N2 (g) + 2O2 (g) à 2NO2 (g) ∆H = 66.4 kJ 2NO (g) + O2 (g) à 2NO2 (g) ∆H = -114.2 kJ the enthalpy of the reaction of nitrogen to produce nitric oxide N2 (g) + O2 (g) à 2NO (g) is __________ kJ. A) 180.6 B) –47.8 C) 47.8 D) –180.6 26. Given the data in the table below, ∆H˚ for the reaction 2CO (g) + O2 (g) à 2CO2 (g) is __________ kJ. Substance ∆Hf˚ (kJ/mol) CO (g) -110.5 CO2 (g) -393.5 CaCO3 (s) -1207.1 A) –677.0 B) 283.3 C) –283.0 D) –566.0

What is the formula for calculating the change in internal energy (ΔE) of a system according to the first law of thermodynamics?

ΔE = q + w, where q is heat and w is work.

How is the heat (q) classified when a system releases heat?

The heat (q) is classified as negative.

What is ΔH for an endothermic process?

ΔH is positive for an endothermic process.

What is ΔH for an exothermic process?

ΔH is negative for an exothermic process.

How do you calculate the heat released when 12.0 g of CO reacts completely, given ΔH˚ = –283 kJ for the reaction CO + O2 → CO2?

Heat released is calculated as q = n * ΔH, where n is the number of moles of CO.

What is the molar mass of CO and how is it used to find moles when calculating the heat released?

The molar mass of CO is approximately 28.0 g/mol. Use it to convert grams of CO to moles.

What is Hess's Law in relation to calculating enthalpy changes?

Hess's Law states that the total enthalpy change of a reaction is the sum of the enthalpy changes of individual steps.

Calculate the enthalpy change for the reaction N2 + O2 → 2NO using the provided reactions and Hess's Law. What is the result?

The enthalpy change for the reaction is 180.6 kJ.

What is the standard enthalpy change (ΔHrxn) formula when using the standard enthalpy of formation data?

ΔHrxn = ΣΔHf,products - ΣΔHf,reactants.

How is the standard enthalpy of formation of elements in their standard state treated in calculations?

It is treated as zero.

What is the total enthalpy change (ΔHrxn) for the reaction 2CO + O2 → 2CO2 according to the provided data?

ΔHrxn = -566.0 kJ.