Question 1

A student collects hydrogen gas over water at 25°C. The total pressure in the collection flask is 745.6 mmHg, and the vapor pressure of water at 25°C is 19.5 mmHg. What is the partial pressure of the hydrogen gas collected?

Accepted Answer

$$726.1\ 	ext{mmHg}$$

Question 2

Which of the following best explains why the dissolution of $$\mathrm{NH_4NO_3} in $$water is endothermic?

Accepted Answer

The energy required to break solute-solute and solvent-solvent interactions is greater than the energy released when solute-solvent interactions form.

Question 3

A student adds $$\mathrm{NH_4NO_3} to $$water and observes the temperature drop from $$24.8^\circ\mathrm{C} to$$ $$22.2^\circ\mathrm{C}. $$What is the value of $$\Delta T$$ for this process?

Accepted Answer

$$-2.6^\circ\mathrm{C}$$

Question 4

Which of the following statements best explains why $$\mathrm{Li}$$ has a lower first ionization energy than $$\mathrm{Be}$$?

Accepted Answer

Li has a longer radius and a lower effective nuclear charge compared to Be.

Question 5

A student heats $$1.50\ \mathrm{kg} of $$sand ($$c = 0.810\ \mathrm{J/g}^\circ\mathrm{C}) $$from $$25.0^\circ\mathrm{C} to$$ $$180.0^\circ\mathrm{C}. $$How much heat is required?

Accepted Answer

$$240,570\ \mathrm{J}$$

Question 6

Which of the following best describes why $$\mathrm{K}$$ has a lower second ionization energy than $$\mathrm{Ca}$$?

Accepted Answer

The second electron removed from K comes from the core electrons, which are closer to the nucleus and experience higher attraction.

Question 7

Which of the following compounds would have the highest boiling point due to intermolecular forces?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} ($$glucose)

Question 8

A student calculates the amount of butane ($$\mathrm{C_4H_{10}}) $$needed to heat $$1.50\ \mathrm{kg} of $$sand from $$25.0^\circ\mathrm{C} to$$ $$180.0^\circ\mathrm{C}. If $$the enthalpy of combustion of butane is $$-2,870\ \mathrm{kJ/mol}$$, how many grams of butane are required?

Accepted Answer

$$5.10\ \mathrm{g}$$

Question 9

Which of the following best explains why $$\mathrm{Br_2$}$$ has a higher boiling point than $$\mathrm{Cl_2$}$$?

Accepted Answer

Br$$_2$$ has more electrons, making it more polarizable and resulting in stronger London dispersion forces.

Question 10

Which of the following is the correct balanced equation for the reaction of zinc with hydrochloric acid?

Accepted Answer

$$\mathrm{Zn} + 2\mathrm{HCl} \rightarrow \mathrm{$$ZnCl_2$$} + \mathrm{H_2$}$$

Question 11

A gas is collected over water at $$25^\circ\mathrm{C}$$ and the atmospheric pressure is $$748.0\ \mathrm{mmHg}. $$The vapor pressure of water at this temperature is $$23.8\ \mathrm{mmHg}. $$What is the pressure of the dry gas?

Accepted Answer

$$724.2\ \mathrm{mmHg}$$

Question 12

Which of the following best explains why the molar mass of an unknown gas can be determined using the ideal gas law?

Accepted Answer

The ideal gas law relates pressure, volume, temperature, and moles, allowing calculation of molar mass if the mass and volume of the gas are known.

Question 13

Which of the following statements is true regarding the energy changes in an endothermic reaction?

Accepted Answer

The system absorbs energy from the surroundings, resulting in a temperature decrease.

Question 14

Which of the following best explains why the bond in $$\mathrm{C_2H_2} is $$stronger than in $$\mathrm{C_2H_4}$$?

Accepted Answer

A triple bond in $$\mathrm{C_2H_2} is $$stronger than the double bond in $$\mathrm{C_2H_4}$$ due to more shared electrons.

General Chemistry: Chemical Reactions, Gas Laws, Thermochemistry, and Periodic Trends

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