Q: Which of the following is the correct balanced chemical equation for the reaction of sodium hydroxide with aluminum to produce hydrogen gas?

$$2\text{NaOH}(aq) + 2\text{Al}(s) + 6\text{H}_2\text{O}(l) \rightarrow 2\text{NaAl(OH)}_4(aq) + 3\text{H}_2(g)$$

Question 1

Which of the following best explains why the ionic radius of Na$$^+ is $$smaller than that of Cl$$^-$$?

Accepted Answer

Na$$^+$$ has more protons than Cl$$^-$$, resulting in a stronger attraction between nucleus and electrons.

Question 2

Which set of hybrid orbitals is used by the central atom in a molecule with square planar geometry?

Accepted Answer

$$dsp^2$$

Question 3

A flask containing 500 mL of water is heated over a Bunsen burner. The temperature of the water increased from 20 $$^	ext{o}C to 85$$ $$^	ext{o}C. $$How much heat did the water absorb? (Specific heat of water = $$4.184 	ext{ J/g}^	ext{o}	ext{C})$$

Accepted Answer

$$66.9 kJ$$

Question 4

Which of the following molecules would you expect to have the lowest rate of effusion?

Accepted Answer

SF$$_6$$

Question 5

Which of the following best describes the geometry and bond angles of a set of $$sp^3d$ hybrid orbitals?

Accepted Answer

Trigonal bipyramidal, 90$$^	ext{o}$$ and 120$$^	ext{o}$$

Question 6

Which of the following is the correct expression for the enthalpy change ($$	riangle H) of a $$reaction?

Accepted Answer

$$	riangle H = H_	ext{products} - H_	ext{reactants}$$

Question 7

Which of the following statements about Graham's Law of Effusion is correct?

Accepted Answer

The rate of effusion of a gas is inversely proportional to the square root of its molar mass.

Question 8

Which of the following is the correct balanced chemical equation for the reaction of sodium hydroxide with aluminum to produce hydrogen gas?

Accepted Answer

$$2	ext{NaOH}(aq) + 2	ext{Al}(s) + 6	ext{H}_2	ext{O}(l) ightarrow 2	ext{NaAl(OH)}_4(aq) + 3	ext{H}_2(g)$$

Question 9

Which of the following is the correct formula for the effective nuclear charge ($$Z_{eff}) $$experienced by a valence electron?

Accepted Answer

$$Z_{eff} = Z - S$$

Question 10

Which of the following best explains why the atomic radius decreases across a period from left to right?

Accepted Answer

Increasing nuclear charge pulls electrons closer to the nucleus.

Question 11

Which of the following is the correct expression for the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 12

A balloon contains 0.076 mol O$$_2$$, 0.031 mol N$$_2$$, and 0.026 mol H$$_2 at 759 mm Hg. $$What is the partial pressure of O$$_2$$?

Accepted Answer

$$399 mm Hg$$

Question 13

Which of the following is the correct definition of enthalpy?

Accepted Answer

The heat content of a system at constant pressure.

Question 14

Which of the following is the correct standard enthalpy of formation ($$	riangle H_f^	ext{o}) $$for CHCl$$_3(l$$)?

Accepted Answer

$$C(s) + rac{1}{2}H_2$(g) + rac{3}{2}Cl_2$(g) ightarrow $$CHCl_3$$(l)$$

Question 15

Which of the following statements about molecular orbital (MO) theory is correct?

Accepted Answer

Bonding molecular orbitals are lower in energy than the atomic orbitals from which they are formed.

Question 16

Which of the following is the correct expression for the first law of thermodynamics?

Accepted Answer

$$	riangle E = q + w$$

Question 17

Which of the following is a consequence of the kinetic molecular theory of gases?

Accepted Answer

The average kinetic energy of gas particles is proportional to the Kelvin temperature.

Question 18

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

Accepted Answer

$$q = m c 	riangle T$$

Question 19

Which of the following is the correct expression for the bond order in molecular orbital theory?

Accepted Answer

$$	ext{Bond order} = \frac{1}{2}(	ext{number of bonding electrons} - 	ext{number of antibonding electrons})$$

Exam III Review

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