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 that can be tested, while a scientific theory is a well-substantiated explanation based on a body of evidence.

Question 2

Which of the following is an example of a heterogeneous mixture?

Accepted Answer

A salad with lettuce, tomatoes, and cucumbers.

Question 3

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 2.00 g. Which statement best describes the measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 4

Which of the following best represents a chemical change?

Accepted Answer

Iron rusting in moist air.

Question 5

Which law states that a chemical compound always contains the same proportion of elements by mass?

Accepted Answer

Law of Definite Proportions

Question 6

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

Accepted Answer

$$0.500$$ moles

Question 7

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 8

Which of the following is the correct electron configuration for a neutral atom of sodium (Na, atomic number 11)?

Accepted Answer

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

Question 9

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have completely filled valence electron shells.

Question 10

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 11

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 12

Which of the following is the correct name for the compound $$Fe_2O_3$$?

Accepted Answer

Iron(III) oxide

Question 13

A sample of water is heated from 25.0 $$^\circC to 75.0$$ $$^\circC. $$What is the temperature change in Kelvin?

Accepted Answer

$$50.0 K$$

Question 14

Which of the following is the correct formula for ammonium sulfate?

Accepted Answer

$$(NH_4$)_2SO_4$$

Question 15

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

Accepted Answer

A physical property can be observed without changing the substance's identity, while a chemical property describes how a substance reacts to form new substances.

Question 16

Which of the following is the correct molar mass of calcium nitrate, $$Ca(NO_3$)_2$$? (Atomic masses: Ca = 40.1, N = 14.0, O = 16.0)

Accepted Answer

$$164.1 g/$$mol

Question 17

Which of the following statements about Avogadro's number is correct?

Accepted Answer

It is the number of particles in one mole of a substance.

Question 18

Which of the following is a correct example of a chemical formula for a molecular compound?

Accepted Answer

$$CO_2$$

Question 19

A 10.0 g sample of a compound contains 4.0 g of hydrogen and 6.0 g of carbon. What is the percent by mass of hydrogen in the compound?

Accepted Answer

$$40\%$$

Question 20

Which of the following is the correct name for $$P_2O_5$$?

Accepted Answer

Diphosphorus pentoxide

General Chemistry I: Study Guide – Matter, Measurement, Atoms, and Compounds

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