Q: A sample of a compound contains 40.0 g of carbon and 6.71 g of hydrogen. What is the percent composition by mass of hydrogen in the compound?

$$\frac{6.71}{40.0 + 6.71} \times 100 = 14.4\%$$

Q: A gas sample has a pressure of 2.00 atm, a volume of 5.00 L, and a temperature of 300 K. How many moles of gas are present? ($$R = 0.0821 L$$·atm/mol·K)

$$n = \frac{PV}{RT} = \frac{2.00 \times 5.00}{0.0821 \times 300} = 0.406$$ moles

Q: A 50.0 g sample of water is heated from 25.0 $$^\circC to 75.0$$ $$^\circC. $$What is the amount of heat absorbed? (Specific heat of water $$c = 4.18 J/g$$·K)

$$q = mc\Delta T = 50.0 \times 4.18 \times (75.0 - 25.0) = 10,450 J$$

Question 1

Which of the following statements best distinguishes a physical change from a chemical change?

Accepted Answer

A physical change involves a change in state or appearance without altering the substance's identity, while a chemical change results in the formation of new substances.

Question 2

A sample of a compound contains 40.0 g of carbon and 6.71 g of hydrogen. What is the percent composition by mass of hydrogen in the compound?

Accepted Answer

$$\frac{6.71}{40.0 + 6.71} 	imes 100 = 14.4\%$$

Question 3

Which of the following best describes the electron configuration of a chloride ion ($$\mathrm{Cl^-}$$)?

Accepted Answer

It has the same electron configuration as argon.

Question 4

A 25.0 g sample of ethanol ($$\mathrm{C_2H_5OH}$$, molar mass = 46.07 g/mol) is combusted. How many moles of ethanol are present in the sample?

Accepted Answer

$$\frac{25.0}{46.07} = 0.543$$ moles

Question 5

Which of the following elements is most likely to form a $$+2$$ ion?

Accepted Answer

Magnesium

Question 6

A solution is prepared by dissolving 10.0 g of NaCl (molar mass = 58.44 g/mol) in enough water to make 500.0 mL of solution. What is the molarity of the solution?

Accepted Answer

$$\frac{10.0}{58.44} = 0.171$$ moles; $$M = \frac{0.171}{0.500} = 0.342 M$$

Question 7

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

Accepted Answer

The effective nuclear charge ($$Z^*) $$increases, pulling electrons closer to the nucleus.

Question 8

A gas sample has a pressure of 2.00 atm, a volume of 5.00 L, and a temperature of 300 K. How many moles of gas are present? ($$R = 0.0821 L$$·atm/mol·K)

Accepted Answer

$$n = \frac{PV}{RT} = \frac{2.00 	imes 5.00}{0.0821 	imes 300} = 0.406$$ moles

Question 9

Which of the following is a correct net ionic equation for the reaction between aqueous solutions of silver nitrate and sodium chloride?

Accepted Answer

$$\mathrm{Ag^+ (aq) + Cl^- (aq) \rightarrow AgCl (s)}$$

Question 10

Which of the following statements about the first law of thermodynamics is correct?

Accepted Answer

The total energy of an isolated system remains constant; energy can be transferred as heat or work.

Question 11

A 50.0 g sample of water is heated from 25.0 $$^\circC to 75.0$$ $$^\circC. $$What is the amount of heat absorbed? (Specific heat of water $$c = 4.18 J/g$$·K)

Accepted Answer

$$q = mc\Delta T = 50.0 	imes 4.18 	imes (75.0 - 25.0) = 10,450 J$$

Question 12

Which of the following best describes Hund’s rule?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing up.

Question 13

Which of the following molecules has a trigonal planar molecular geometry?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 14

A sample of gas at 25 $$^\circC $$occupies 2.00 L. What volume will it occupy at 50 $$^\circC$$, assuming constant pressure? (Use Charles’s Law)

Accepted Answer

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 2.00 	imes \frac{323}{298} = 2.17$$ L

Question 15

Which of the following is the correct electron configuration for a ground-state calcium atom ($$Z=20$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$

Question 16

Which of the following statements about redox reactions is correct?

Accepted Answer

Oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 17

A 0.100 M solution of HCl has a $$[OH^-] of$$ $$1.0 	imes 10$$^{-13}$$ M. What is the pH of the solution?

Accepted Answer

$$pH = -\log(0.100) = 1.00$$

Question 18

Which of the following best describes the relationship between wavelength ($$\lambda) $$and frequency ($$v) of $$light?

Accepted Answer

$$c = \lambda v$$, so as wavelength increases, frequency decreases.

Question 19

Which of the following is the correct Lewis structure for the nitrate ion ($$\mathrm{NO_3$^-}$$)?

Accepted Answer

Three resonance structures, each with one N=O double bond and two N–O single bonds, with a negative charge delocalized over the oxygens.

General Chemistry Final Exam Review: Comprehensive Study Notes

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