Question 1

Which of the following statements best describes the difference between precision and accuracy in scientific measurements?

Accepted Answer

Precision refers to how close measurements are to each other, while accuracy refers to how close measurements are to the true value.

Question 2

A student measures the mass of a sample as 0.00450 g. How many significant figures are in this measurement?

Accepted Answer

3

Question 3

Which of the following is the correct conversion of 25.0 °C to Kelvin?

Accepted Answer

$$K = ^\circ C + 273.15 = 25.0 + 273.15 = 298.15\ K$$

Question 4

Which of the following is a physical change?

Accepted Answer

Melting of ice

Question 5

Which of the following is a heterogeneous mixture?

Accepted Answer

Sand and iron filings

Question 6

Which of the following is a diatomic molecule?

Accepted Answer

$$O_2$$

Question 7

Which group in the periodic table contains the noble gases?

Accepted Answer

Group 18

Question 8

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

Accepted Answer

$$CH_2O$$

Question 9

Which of the following ions has a charge of +2?

Accepted Answer

$$Cu^{2+}$$

Question 10

Which law states that mass is neither created nor destroyed in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 11

A sample contains 80.0 g of water ($$H_2O). $$How many moles of water are present? ($$M_{H_2O} = 18.0\ g/mol)$$

Accepted Answer

$$4.44\ mol$$

Question 12

Which of the following best describes an element?

Accepted Answer

A pure substance consisting of only one type of atom.

Question 13

Which of the following is the correct formula for the polyatomic ion phosphate?

Accepted Answer

$$PO_4$$^{3-}$$

Question 14

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 15

Which of the following is the correct formula for calculating density?

Accepted Answer

$$Density = \frac{mass}{volume}$$

Question 16

A solution is prepared by dissolving 5.00 g of NaCl in enough water to make 250.0 mL of solution. What is the concentration of NaCl in $$g/L$$?

Accepted Answer

$$20.0\ g/L$$

Question 17

Which of the following is a transition metal?

Accepted Answer

Iron

Question 18

Which of the following is the correct formula for Avogadro's number?

Accepted Answer

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

Question 19

Which of the following is the correct name for $$FeCl_3$$?

Accepted Answer

Iron(III) chloride

Question 20

A sample contains two isotopes of chlorine: $$^{35}Cl (75.8$$% abundance, mass = 34.97 u) and $$^{37}Cl (24.2$$% abundance, mass = 36.97 u). What is the average atomic mass of chlorine?

Accepted Answer

$$35.45\ u$$

General Chemistry Fundamentals: Measurement, Matter, Atomic Theory, and Chemical Nomenclature

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