Q: Which of the following is the correct formula for calculating the percent yield of a chemical reaction?

$$\text{Percent yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100$$

Question 1

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

Accepted Answer

The effective nuclear charge increases, pulling electrons closer to the nucleus.

Question 2

A sample contains 22.8% sodium, 21.8% boron, and 55.4% oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{$$NaBO_2$$}$$

Question 3

Which of the following species contains both covalent and ionic bonds?

Accepted Answer

$$\mathrm{Na_2SO_4}$$

Question 4

A 0.52 g sample of sodium acetate is dissolved in water and diluted to 100.0 mL. What is the molarity of the solution? (Molar mass of sodium acetate = $$82.0\ \mathrm{g\ $$mol^{-1}$$})$$

Accepted Answer

$$0.063\ \mathrm{M}$$

Question 5

Which of the following best describes the hybridization of the central atom in $$\mathrm{CO_2$}$$?

Accepted Answer

$$sp$$

Question 6

A student determines the percent water in a sample with the following values: 16.145%, 16.160%, 16.156%, and 17.299%. What should be reported as the percent water?

Accepted Answer

16.15% (excluding the outlier 17.299%)

Question 7

Which of the following ions has the largest radius?

Accepted Answer

$$\mathrm{Cl^-}$$

Question 8

Which of the following statements is true regarding the Law of Conservation of Mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 9

Which of the following best explains why water has a higher boiling point than methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

Water molecules form hydrogen bonds, which require more energy to break.

Question 10

Which of the following is the correct ground-state electron configuration for the element in Period 3, Group 3A?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^1$$

Question 11

Which of the following is the correct balanced equation for the reaction of iron metal with oxygen to form iron(III) oxide?

Accepted Answer

$$4\mathrm{Fe} + 3\mathrm{O}_2 \rightarrow 2\mathrm{Fe}_2\mathrm{O}_3$$

Question 12

Which of the following molecules is expected to have the largest dipole moment?

Accepted Answer

$$\mathrm{H_2O}$$

Question 13

A mercury manometer is used to measure the pressure of a trapped gas. The atmospheric pressure is 749 mmHg and the mercury column is 21 mm higher on the open side. What is the pressure of the trapped gas?

Accepted Answer

$$770\ \mathrm{mmHg}$$

Question 14

Which of the following best describes the shape of the $$\mathrm{NH_3$}$$ molecule?

Accepted Answer

Trigonal pyramidal

Question 15

Which of the following statements about limiting reactants is correct?

Accepted Answer

The limiting reactant is the one that is completely consumed first in a chemical reaction.

Question 16

Which of the following best explains why ionic compounds tend to have high melting points?

Accepted Answer

Strong electrostatic forces between oppositely charged ions require a large amount of energy to break.

Question 17

Which of the following is the correct formula for calculating the percent yield of a chemical reaction?

Accepted Answer

$$	ext{Percent yield} = \frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100$$

Question 18

Which of the following best describes the process of dissolving table salt ($$\mathrm{NaCl}) in $$water?

Accepted Answer

The $$\mathrm{Na^+}$$ and $$\mathrm{Cl^-}$$ ions are surrounded by water molecules, which stabilize them in solution.

Question 19

Which of the following is the correct expression for the enthalpy change ($$\Delta H) of a $$reaction using bond energies?

Accepted Answer

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

General Chemistry I: Comprehensive Study Notes (CHEM 120 Final Exam Practice Questions)

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