Question 1

When burning wood in an open fireplace, the chemical reaction of wood combustion primarily produces carbon dioxide and water. If the enthalpy of combustion of wood is approximately $$18\,\mathrm{MJ/kg}$$, how much wood (in kg) must be burned to produce $$72\,\mathrm{MJ} of $$heat?

Accepted Answer

$$4.0\,\mathrm{kg}$$

Question 2

Which of the following molecules will have the largest value of the van der Waals 'a' parameter, which reflects the strength of intermolecular attractions?

Accepted Answer

Water ($$\mathrm{H}_2\mathrm{O})$$

Question 3

A sample of copper at $$80.0\,^{\circ}\mathrm{C} is $$placed in $$100.0\,\mathrm{g} of $$water at $$24.0\,^{\circ}\mathrm{C}. If $$the final temperature is $$27.1\,^{\circ}\mathrm{C}$$, what is the specific heat capacity $$c of $$copper? (Assume $$c_{\mathrm{H}_2$$\mathrm{O}} = 4.18\,\mathrm{J/g\$$cdot ^{\circ}C$$}$$ and mass of copper is 50.0$$\,\mathrm{g}$$)

Accepted Answer

$$0.39\,\mathrm{J/g\$$cdot ^{\circ}$$C}$$

Question 4

The complete combustion reaction of propane ($$\mathrm{C}_3\mathrm{H}_8) is$$ $$\mathrm{C}_3\mathrm{H}_8 + 5\mathrm{O}_2 \rightarrow 3\mathrm{CO}_2 + 4\mathrm{H}_2\mathrm{O}$$, $$\Delta H = -2043\,\mathrm{kJ}. $$How much heat is released when $$2.00\,\mathrm{mol} of $$propane is combusted?

Accepted Answer

$$-4086\,\mathrm{kJ}$$

Question 5

A tile used on the space shuttle is made mostly of $$\mathrm{SiO}_2$$ and has a mass of $$1.5\,\mathrm{kg}. If $$the specific heat capacity of $$\mathrm{SiO}_2 is$$ $$0.84\,\mathrm{J/g\$$cdot ^{\circ}$$C}$$, how much heat is required to raise the temperature of the tile from $$20.0\,^{\circ}\mathrm{C} to$$ $$1200.0\,^{\circ}\mathrm{C}$$?

Accepted Answer

$$1,494,000\,\mathrm{J}$$

Question 6

During a chemical reaction, $$75\,\mathrm{J} of $$energy is transferred to the surroundings as heat. The initial and final temperature of the surroundings are measured as $$22.5\,^{\circ}\mathrm{C}$$ and $$27.1\,^{\circ}\mathrm{C}$$, respectively. What is the heat capacity $$C (in$$ $$\mathrm{J}$$/^{\circ}$$\mathrm{C}) of $$the surroundings?

Accepted Answer

$$16.3\,\mathrm{J}$$/^{\circ}$$\mathrm{C}$$

Question 7

Which statement best explains why oxygen ($$\mathrm{O}_2) $$and water ($$\mathrm{H}_2\mathrm{O}) $$have similar values of van der Waals 'a' but different van der Waals 'b' constants?

Accepted Answer

They have similar intermolecular attractions but different molecular sizes.

Question 8

A sample of liquid ethanol has a heat capacity $$C = 2.57\,\mathrm{J}$$/^{\circ}$$\mathrm{C}$$ and a mass of $$1.00\,\mathrm{g}. $$What is the molar heat capacity $$C_m in$$ $$\mathrm{J}/\mathrm{mol}\$$cdot ^{\circ}$$\mathrm{C}$$? (Molar mass of ethanol $$= 46.07\,\mathrm{g}/\mathrm{mol})$$

Accepted Answer

$$118\,\mathrm{J}/\mathrm{mol}\$$cdot ^{\circ}$$\mathrm{C}$$

Question 9

The approximate mean free path of propane ($$\mathrm{C}_3\mathrm{H}_8) $$molecules at STP is $$113\,\mathrm{nm}. $$What is the effective diameter $$d of a $$propane molecule in picometers (pm)? Use $$\lambda = \frac{k_B T}{\sqrt{2} \pi d^2$ P}$$ and $$k_B = 1.38 	imes 10$$^{-23}$$\,\mathrm{J/K}$$, $$T = 273\,\mathrm{K}$$, $$P = 1.01 	imes 10^5$\,\mathrm{Pa}.$$

Accepted Answer

$$430\,\mathrm{pm}$$

Question 10

Consider the decomposition reaction of calcium carbonate: $$\mathrm{CaCO}_3 (s) \rightarrow \mathrm{CaO} (s) + \mathrm{CO}_2 (g). $$Which of the following best describes the sign of $$\Delta S$$ and $$\Delta H$$ for this reaction?

Accepted Answer

$$\Delta S \u003e 0$$, $$\Delta H \u003e 0$$

Question 11

A space shuttle tile has a mass of $$500\,\mathrm{kg}$$ and the total heat absorbed is $$900\,\mathrm{kJ}. $$What is the total heat capacity $$C (in$$ $$\mathrm{J}$$/^{\circ}$$\mathrm{C}) if $$the temperature change is $$20.0\,^{\circ}\mathrm{C}$$?

Accepted Answer

$$45\,\mathrm{J}$$/^{\circ}$$\mathrm{C}$$

Question 12

Which of the following best describes the behavior of all gases at STP (standard ambient temperature and pressure)?

Accepted Answer

They occupy the same molar volume and behave ideally.

Question 13

The temperature in space, before re-entry, is $$2.7\,\mathrm{K}. $$Assuming that the tile starts at this temperature, what is the minimum amount of heat (in J) that can be absorbed by the tile before it becomes damaged if the damage threshold is $$1200\,^{\circ}\mathrm{C}$$ and the tile mass is $$1.5\,\mathrm{kg}$$ with $$c = 0.84\,\mathrm{J/g\$$cdot ^{\circ}$$C}$$?

Accepted Answer

$$1,504,000\,\mathrm{J}$$

Question 14

Consider the reaction: $$2\mathrm{Ag}_2\mathrm{O} (s) ightarrow 4\mathrm{Ag} (s) + \mathrm{O}_2 (g)$$, $$\Delta H = 2.00 	imes 10^2$\,\mathrm{kJ}$$ and $$\Delta S = 218.1\,\mathrm{J/K}. $$Calculate the least at which reaction is spontaneous ($$T_{min}) in $$Kelvin.

Accepted Answer

$$917\,\mathrm{K}$$

Question 15

Which of the following statements about the heat of the surroundings for an exothermic reaction is correct?

Accepted Answer

The heat of the surroundings increases as the system releases energy.

Question 16

If the pressure exerted by a real gas is less than that predicted by the ideal gas law, which factor is most likely responsible?

Accepted Answer

Intermolecular attractions between gas molecules.

Question 17

A scientist is designing a heat shield for a spacecraft using $$\mathrm{Li}_2\mathrm{SiO}_3$$ tiles. If the tiles are $$4.0\,\mathrm{cm} 	imes 4.0\,\mathrm{cm} 	imes 1.0\,\mathrm{cm}$$ and the density of $$\mathrm{Li}_2\mathrm{SiO}_3 is$$ $$2.54\,\mathrm{g/cm}^3$$, what is the mass of one tile?

Accepted Answer

$$40.6\,\mathrm{g}$$

Question 18

Which of the following best explains why the energy content of wood and propane differ when burned for heat?

Accepted Answer

Propane has a higher energy density due to its chemical structure.

General Chemistry Study Guide: Thermochemistry, Gases, and Related Calculations

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