Q: A sample contains 3.00 moles of sodium chloride ($$NaCl). $$What is the mass of this sample in grams? ($$M_{NaCl} = 58.44 \ g/mol)$$

$$3.00 \times 58.44 = 175.32 \ g$$

Q: A reaction has a theoretical yield of 10.0 g, but only 7.5 g of product is obtained. What is the percent yield?

$$\frac{7.5}{10.0} \times 100 = 75\%$$

Q: Which of the following is the correct formula for calculating the average atomic mass of an element?

$$\text{Average atomic mass} = \sum (\text{isotope mass} \times \text{fractional abundance})$$

Q: A student needs to prepare 500.0 mL of a 0.250 M $$KBr$$ solution. How many grams of $$KBr$$ are required? ($$M_{KBr} = 119.0 \ g/mol)$$

$$0.250 \times 0.500 \times 119.0 = 14.9 \ g$$

Question 1

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

Accepted Answer

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

Question 2

A sample contains 3.00 moles of sodium chloride ($$NaCl). $$What is the mass of this sample in grams? ($$M_{NaCl} = 58.44 \ g/mol)$$

Accepted Answer

$$3.00 	imes 58.44 = 175.32 \ g$$

Question 3

Which scientist is credited with discovering the electron using the cathode ray tube experiment?

Accepted Answer

J.J. Thomson

Question 4

Which of the following is the correct balanced chemical equation for the combustion of methane ($$CH_4) in $$oxygen?

Accepted Answer

$$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$

Question 5

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

$$CH_2O$$

Question 6

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 7

A student dissolves 5.00 g of $$NaOH in $$enough water to make 250.0 mL of solution. What is the molarity of the solution? ($$M_{NaOH} = 40.00 \ g/mol)$$

Accepted Answer

$$0.200 \ mol/L$$

Question 8

Which of the following elements is classified as a metalloid?

Accepted Answer

Silicon ($$Si)$$

Question 9

Which of the following is NOT a correct statement about the periodic table?

Accepted Answer

Metals are generally found on the right side of the periodic table.

Question 10

A reaction has a theoretical yield of 10.0 g, but only 7.5 g of product is obtained. What is the percent yield?

Accepted Answer

$$\frac{7.5}{10.0} 	imes 100 = 75\%$$

Question 11

Which of the following is a molecular compound?

Accepted Answer

Carbon dioxide ($$CO_2)$$

Question 12

Which of the following best describes the law of definite proportions?

Accepted Answer

A compound always contains the same elements in the same ratio by mass.

Question 13

Which of the following is the correct formula for calculating the average atomic mass of an element?

Accepted Answer

$$	ext{Average atomic mass} = \sum (	ext{isotope mass} 	imes 	ext{fractional abundance})$$

Question 14

Which of the following is the correct net ionic equation for the reaction between aqueous $$Na_2SO_4$$ and $$BaCl_2$$?

Accepted Answer

$$Ba^{2+}(aq$$) + $$SO_4$$^{2-}(aq) \rightarrow $$BaSO_4(s$$)$$

Question 15

A student needs to prepare 500.0 mL of a 0.250 M $$KBr$$ solution. How many grams of $$KBr$$ are required? ($$M_{KBr} = 119.0 \ g/mol)$$

Accepted Answer

$$0.250 	imes 0.500 	imes 119.0 = 14.9 \ g$$

Question 16

Which of the following is the correct electron configuration for a neutral atom of oxygen ($$O$$)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^4$$

Question 17

Which of the following is the correct formula for calculating density?

Accepted Answer

$$	ext{Density} = \frac{	ext{mass}}{	ext{volume}}$$

Question 18

Which of the following is a correct statement about ionic compounds?

Accepted Answer

They are composed of cations and anions held together by electrostatic forces.

Question 19

Which of the following is the correct formula for calculating molarity?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}$$

General Chemistry I: Study Guide for Exam 1 (Chapters 1–4)

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