Q: A student measures the mass of a sample as 2.50 g using a balance with an uncertainty of ±0.05 g. What is the percent uncertainty of the measurement?

$ \frac{0.05}{2.50} \times 100 = 2\% $

Q: A sample of gas at 1.00 atm and 273 K occupies 22.4 L. If the pressure is doubled and the temperature is kept constant, what will be the new volume?

$ V_2 = \frac{P_1 V_1}{P_2} = \frac{1.00 \times 22.4}{2.00} = 11.2\ \mathrm{L} $

Question 1

Which of the following best describes a chemical change?

Accepted Answer

Iron rusting when exposed to air

Question 2

A student measures the mass of a sample as 2.50 g using a balance with an uncertainty of ±0.05 g. What is the percent uncertainty of the measurement?

Accepted Answer

$ \frac{0.05}{2.50} 	imes 100 = 2\% $

Question 3

Which statement about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 4

Which of the following is a heterogeneous mixture?

Accepted Answer

Sand and iron filings

Question 5

A compound contains 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$ \mathrm{CH_2O} $

Question 6

Which of the following best explains why water is a polar molecule?

Accepted Answer

Water has a bent molecular shape and oxygen is more electronegative than hydrogen.

Question 7

Which equation correctly relates the energy of a photon to its frequency?

Accepted Answer

$ E = h 
u $

Question 8

A solution is prepared by dissolving 5.00 g of NaCl in enough water to make 250 mL of solution. What is the molarity of the solution? ($ \mathrm{NaCl} $ molar mass = 58.44 g/mol)

Accepted Answer

$ \frac{5.00\ \mathrm{g}}{58.44\ \mathrm{g/mol}} = 0.0856\ \mathrm{mol};\ \frac{0.0856\ \mathrm{mol}}{0.250\ \mathrm{L}} = 0.342\ \mathrm{M} $

Question 9

Which of the following is the correct electron configuration for a neutral atom of sulfur ($ Z = 16 $)?

Accepted Answer

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

Question 10

Which of the following best describes the difference between a physical and a chemical change?

Accepted Answer

A chemical change results in the formation of new substances, while a physical change does not.

Question 11

Which of the following is the correct balanced equation for the combustion of methane ($ \mathrm{CH_4} $)?

Accepted Answer

$ \mathrm{CH_4} + 2\mathrm{O_2} \rightarrow \mathrm{CO_2} + 2\mathrm{H_2O} $

Question 12

Which of the following statements about acids and bases is true according to the Brønsted-Lowry definition?

Accepted Answer

An acid is a proton donor and a base is a proton acceptor.

Question 13

Which of the following best describes the relationship between heat, work, and total energy change in a system?

Accepted Answer

$ \Delta E = q + w $

Question 14

A sample of gas at 1.00 atm and 273 K occupies 22.4 L. If the pressure is doubled and the temperature is kept constant, what will be the new volume?

Accepted Answer

$ V_2 = \frac{P_1 V_1}{P_2} = \frac{1.00 	imes 22.4}{2.00} = 11.2\ \mathrm{L} $

Question 15

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

Accepted Answer

$ \mathrm{BF_3} $

Question 16

Which of the following is the correct net ionic equation for the reaction between $ \mathrm{NaOH} $ and $ \mathrm{HCl} $?

Accepted Answer

$ \mathrm{OH^-} + \mathrm{H^+} \rightarrow \mathrm{H_2O} $

Question 17

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have delocalized electrons that can move freely throughout the structure.

Question 18

Which of the following is the correct formula for calculating the pH of a solution?

Accepted Answer

$ \mathrm{pH} = -\log[\mathrm{H^+}] $

Question 19

A reaction has a rate constant $ k $ that doubles when the temperature increases from 300 K to 310 K. Which equation best describes this relationship?

Accepted Answer

$ k = A e^{-E_a/(RT)} $

Introduction to Chemistry: Comprehensive Study Guide

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