Q: Convert 0.0056 kilometers to centimeters. (1 km = 1000 m, 1 m = 100 cm)

$$0.0056 \text{ km} \times \frac{1000 \text{ m}}{1 \text{ km}} \times \frac{100 \text{ cm}}{1 \text{ m}} = 560 \text{ cm}$$

Q: A sample contains $$3.01 \times 10$$^{23}$$ atoms of carbon. How many moles of carbon are present?

$$\frac{3.01 \times 10$$^{23}$$}{6.022 \times 10$$^{23}$$} = 0.500$$ mol

Q: Calculate the mass percent of hydrogen in water ($$H_2O). ($$Molar mass: H = 1.01 g/mol, O = 16.00 g/mol)

$$\frac{2 \times 1.01}{2 \times 1.01 + 16.00} \times 100\% = 11.2\%$$

Question 1

Which of the following statements best describes the difference between a hypothesis and a scientific theory?

Accepted Answer

A hypothesis is a tentative explanation for an observation, while a scientific theory is a well-substantiated explanation that has been repeatedly tested and confirmed.

Question 2

A sample of a compound contains only sodium and chlorine. Which of the following best classifies this sample?

Accepted Answer

A pure substance, specifically a compound.

Question 3

Which method would be most effective for separating a mixture of sand and saltwater?

Accepted Answer

Filtration followed by distillation.

Question 4

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

Accepted Answer

Iron rusting in moist air.

Question 5

A student measures the mass of a sample three times and obtains values of 5.12 g, 5.13 g, and 5.11 g. The true mass is 5.50 g. Which statement best describes the data?

Accepted Answer

The data are precise but not accurate.

Question 6

Convert 0.0056 kilometers to centimeters. (1 km = 1000 m, 1 m = 100 cm)

Accepted Answer

$$0.0056 	ext{ km} 	imes \frac{1000 	ext{ m}}{1 	ext{ km}} 	imes \frac{100 	ext{ cm}}{1 	ext{ m}} = 560 	ext{ cm}$$

Question 7

Which of the following statements is consistent with Dalton’s Atomic Theory?

Accepted Answer

Atoms of a given element are identical in mass and properties.

Question 8

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

Accepted Answer

Rutherford’s gold foil experiment.

Question 9

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it contain?

Accepted Answer

$$24 - 12 = 12$$ neutrons

Question 10

Which of the following elements is a halogen?

Accepted Answer

Chlorine (Cl)

Question 11

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

Accepted Answer

$$\frac{3.01 	imes 10$$^{23}$$}{6.022 	imes 10$$^{23}$$} = 0.500$$ mol

Question 12

Which of the following best describes the bonding in sodium chloride (NaCl)?

Accepted Answer

Ionic bonding between a metal and a nonmetal.

Question 13

Which of the following is a molecular element?

Accepted Answer

Oxygen ($$O_2)$$

Question 14

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

Accepted Answer

$$CH_2O$$

Question 15

Which of the following names is correct for $$Fe_2O_3$$?

Accepted Answer

Iron(III) oxide

Question 16

Calculate the mass percent of hydrogen in water ($$H_2O). ($$Molar mass: H = 1.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$$\frac{2 	imes 1.01}{2 	imes 1.01 + 16.00} 	imes 100\% = 11.2\%$$

Question 17

A compound is found to contain 4.00 g of hydrogen and 32.00 g of oxygen. What is the empirical formula?

Accepted Answer

$$H_2O$$

Question 18

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 19

Which of the following is an intensive property?

Accepted Answer

Density

Question 20

A sample of ethanol has a density of $$0.789 	ext{ g/mL}. $$What is the mass of $$25.0 	ext{ mL} of $$ethanol?

Accepted Answer

$$0.789 	ext{ g/mL} 	imes 25.0 	ext{ mL} = 19.7 	ext{ g}$$

General Chemistry I: Study Guide for Chapters 1–3

Guida di studio - Domande di pratica

Study guide - Flashcard