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

$$\frac{32.0}{44.0} \times 100 = 72.7\%$$

Question 1

Which of the following best describes a scientific theory?

Accepted Answer

A well-substantiated explanation of some aspect of the natural world that is based on a body of evidence and has stood the test of time.

Question 2

A sample of a compound contains only sodium and chlorine. Which of the following statements is true about this sample?

Accepted Answer

It is a pure substance composed of ions.

Question 3

Which of the following is an example of a physical change?

Accepted Answer

Water boiling to form steam.

Question 4

A student measures the mass of a sample three times and gets values of 2.51 g, 2.50 g, and 2.52 g. The true mass is 2.80 g. Which statement best describes the measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 5

Which of the following correctly expresses the law of definite proportions?

Accepted Answer

A chemical compound always contains exactly the same proportion of elements by mass.

Question 6

A sample of carbon dioxide contains 12.0 g of carbon and 32.0 g of oxygen. What is the mass percent of oxygen in carbon dioxide?

Accepted Answer

$$\frac{32.0}{44.0} 	imes 100 = 72.7\%$$

Question 7

Which experiment provided evidence for the existence of the atomic nucleus?

Accepted Answer

Rutherford's gold foil experiment.

Question 8

How many protons, neutrons, and electrons are in the isotope $$_{17}^{37}\mathrm{Cl}$$?

Accepted Answer

17 protons, 20 neutrons, 17 electrons

Question 9

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 10

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

Accepted Answer

$$0.500$$ mol

Question 11

Which of the following best describes the difference between a molecule and an ionic compound?

Accepted Answer

A molecule is composed of atoms covalently bonded together, while an ionic compound is composed of ions held together by electrostatic forces.

Question 12

Which of the following is the correct empirical formula for a compound containing 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 13

A compound has an empirical formula of $$\mathrm{CH}_2\mathrm{O}$$ and a molar mass of 180 g/mol. What is its molecular formula?

Accepted Answer

$$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$

Question 14

Which of the following is a correct statement about the periodic table?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 15

Which of the following ions is isoelectronic with neon ($$\mathrm{Ne}$$)?

Accepted Answer

$$\mathrm{F}^-$$

Question 16

A student needs to prepare 250.0 mL of a 0.100 M NaCl solution. How many grams of NaCl are required? ($$\mathrm{NaCl}$$ molar mass = 58.44 g/mol)

Accepted Answer

$$0.100 	imes 0.250 	imes 58.44 = 1.46 g$$

Question 17

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

Accepted Answer

They are composed of ions held together by strong electrostatic forces.

Question 18

Which of the following is the correct number of significant figures in the measurement 0.004560 g?

Accepted Answer

4

Question 19

A sample of a compound contains 0.250 mol of carbon, 0.500 mol of hydrogen, and 0.250 mol of oxygen. What is the empirical formula?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 20

Which of the following best describes the difference between a heterogeneous and a homogeneous mixture?

Accepted Answer

A heterogeneous mixture has a non-uniform composition, while a homogeneous mixture has a uniform composition throughout.

General Chemistry Study Guide: Matter, Measurement, Atomic Theory, and Chemical Compounds

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