Q: A sample of a compound contains 12.0 g of carbon and 32.0 g of oxygen. What is the percent composition by mass of carbon in the compound?

$$\frac{12.0}{44.0} \times 100 = 27.3\%$$

Q: Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

$$\text{moles} = \frac{\text{mass}}{\text{molar mass}}$$

Q: If a reaction has a theoretical yield of 10.0 g and an actual yield of 7.5 g, what is the percent yield?

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

Question 1

Which of the following best describes a chemical property?

Accepted Answer

The ability of a substance to react with oxygen to form an oxide

Question 2

A sample of a compound contains 12.0 g of carbon and 32.0 g of oxygen. What is the percent composition by mass of carbon in the compound?

Accepted Answer

$$\frac{12.0}{44.0} 	imes 100 = 27.3\%$$

Question 3

Which statement about Dalton’s Atomic Theory is NOT correct according to modern chemistry?

Accepted Answer

Atoms of the same element are identical in mass and properties

Question 4

A student measures the mass of a sample as 12.30 g and its volume as 4.1 mL. What is the density of the sample, reported with the correct number of significant figures?

Accepted Answer

$$\frac{12.30}{4.1} = 3.0\ \mathrm{g/mL}$$

Question 5

Which of the following is a mixture?

Accepted Answer

Air

Question 6

How many significant figures are in the measurement 0.00450 kg?

Accepted Answer

3

Question 7

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 8

Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

Accepted Answer

$$	ext{moles} = \frac{	ext{mass}}{	ext{molar mass}}$$

Question 9

A chemical reaction is represented as: $$2\mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\mathrm{H_2O}. If $$you start with 4 moles of $$\mathrm{H_2$}$$ and excess $$\mathrm{O_2$}$$, how many moles of $$\mathrm{H_2O}$$ will be produced?

Accepted Answer

4 moles

Question 10

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons

Question 11

Which of the following is the correct value for Avogadro’s number?

Accepted Answer

$$6.022 	imes 10$$^{23}$$

Question 12

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

Accepted Answer

$$\mathrm{CH_2O}$$

Question 13

Which of the following is a polyatomic ion?

Accepted Answer

$$\mathrm{SO_4$^{2-}}$$

Question 14

If a reaction has a theoretical yield of 10.0 g and an actual yield of 7.5 g, what is the percent yield?

Accepted Answer

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

Question 15

Which of the following is the correct balanced equation for the reaction between sodium and chlorine to form sodium chloride?

Accepted Answer

$$2\mathrm{Na} + \mathrm{Cl_2$} \rightarrow 2\mathrm{NaCl}$$

Question 16

Which of the following statements about metals is correct?

Accepted Answer

Metals are malleable and ductile

Question 17

A student needs to convert 25.0 cm to meters. Which of the following is the correct conversion?

Accepted Answer

$$25.0\ \mathrm{cm} 	imes \frac{1\ \mathrm{m}}{100\ \mathrm{cm}} = 0.250\ \mathrm{m}$$

Question 18

Which of the following is the correct formula for calculating percent composition by mass?

Accepted Answer

$$\frac{	ext{mass of element}}{	ext{total mass of compound}} 	imes 100$$

Question 19

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of $$\mathrm{$$CO_2$$}$$. How many moles of $$\mathrm{$$CO_2$$}$$ are present?

Accepted Answer

$$0.5$$ moles

General Chemistry Chapters 1–3: Matter, Measurement, Atoms, and Stoichiometry

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