Question 1

Which of the following statements best describes a chemical change?

Accepted Answer

A substance reacts with oxygen to form a new compound.

Question 2

Which of the following is a heterogeneous mixture?

Accepted Answer

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 2.80 g. Which statement best describes the measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 4

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

Accepted Answer

4

Question 5

Which law is illustrated when 12.0 g of carbon reacts with 32.0 g of oxygen to produce 44.0 g of carbon dioxide?

Accepted Answer

Law of Conservation of Mass

Question 6

Which of the following statements is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms can be converted into other elements during chemical reactions.

Question 7

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 8

An isotope of carbon has 6 protons and 8 neutrons. What is its mass number?

Accepted Answer

$$14$$

Question 9

Which element is most likely to form a $$2^+$$ ion?

Accepted Answer

Magnesium ($$Mg)$$

Question 10

Given the following natural abundances and masses for chlorine isotopes: $$^{35}Cl (75.78$$%, 34.969 amu) and $$^{37}Cl (24.22$$%, 36.966 amu), what is the average atomic mass of chlorine?

Accepted Answer

$$35.45$$ amu

Question 11

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between two nonmetal atoms.

Question 12

Which of the following compounds is an example of a molecular compound?

Accepted Answer

Carbon dioxide ($$CO_2)$$

Question 13

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

Accepted Answer

$$CH_2O$$

Question 14

How many moles are in $$18.0$$ grams of water ($$H_2O$$)? (Molar mass of $$H_2O = 18.0 g/$$mol)

Accepted Answer

$$1.0$$ mol

Question 15

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

Accepted Answer

$$(NH_4$)_2SO_4$$

Question 16

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

Accepted Answer

$$0.50$$ mol

Question 17

Which of the following best explains why water ($$H_2O) is a $$compound and not a mixture?

Accepted Answer

It is composed of two elements chemically combined in a fixed ratio.

Question 18

Which of the following is a physical property?

Accepted Answer

Melting point

Question 19

A student needs to convert $$25.0$$ inches to centimeters. (1 inch = 2.54 cm, exact) What is the correct answer with the proper number of significant figures?

Accepted Answer

$$63.5 cm$$

Question 20

Which of the following best describes the difference between systematic error and random error?

Accepted Answer

Systematic error can be corrected, while random error cannot.

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

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