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

$$\frac{32.0}{12.0+32.0} \times 100 = 72.7\%$$

Q: Which of the following correctly represents the calculation for the average atomic mass of an element with two isotopes?

$$\sum \left( [\text{isotope mass}] \times [\text{fractional isotope abundance}] \right)$$

Q: How many oxygen atoms are present in 2.00 moles of $$\mathrm{CO_2$}$$?

$$2.41 \times 10$$^{24}$$ atoms

Question 1

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

Accepted Answer

Iron rusting in moist air

Question 2

Which of the following ions has a predictable charge of +2 according to its position on the periodic table?

Accepted Answer

$$\mathrm{Ca$$^{2+}$$}$$

Question 3

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

Accepted Answer

$$\frac{32.0}{12.0+32.0} 	imes 100 = 72.7\%$$

Question 4

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

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Question 5

How many significant figures are in the measurement 0.0045600 g?

Accepted Answer

6

Question 6

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture in which the composition is uniform throughout

Question 7

What is the correct name for the ion $$\mathrm{SO_4$^{2-}}$$?

Accepted Answer

Sulfate

Question 8

A student needs to convert 5.00 km to centimeters. Which of the following is the correct answer?

Accepted Answer

$$5.00 	imes 10^5$ cm

Question 9

Which of the following elements is a noble gas?

Accepted Answer

Argon

Question 10

Calculate the number of moles in 18.0 g of water ($$\mathrm{H_2O}). ($$Molar mass of $$\mathrm{H_2O} = 18.0 g/$$mol)

Accepted Answer

$$1.00$$ mol

Question 11

Which of the following ions is polyatomic and has a -1 charge?

Accepted Answer

$$\mathrm{NO_3$^-}$$

Question 12

A sample contains 3.01 $$	imes$$ $$10^{23}$$ atoms of sodium. What is the mass of sodium in the sample? (Molar mass of Na = 23.0 g/mol, Avogadro's number = $$6.02 	imes 10$$^{23}$$ mol$$^{-1}$$)

Accepted Answer

11.5 g

Question 13

Which of the following correctly represents the calculation for the average atomic mass of an element with two isotopes?

Accepted Answer

$$\sum \left( [	ext{isotope mass}] 	imes [	ext{fractional isotope abundance}] ight)$$

Question 14

Which of the following is the correct formula for the compound formed between calcium and nitrate?

Accepted Answer

$$\mathrm{Ca(NO_3$)_2}$$

Question 15

A 250.0 mL sample of ethanol has a mass of 197.5 g. What is the density of ethanol in g/mL?

Accepted Answer

$$0.790 g/mL$$

Question 16

Which of the following is a correct name-symbol pair for an element?

Accepted Answer

Sodium, Na

Question 17

Which of the following best describes an extensive property?

Accepted Answer

A property that depends on the amount of substance present

Question 18

How many oxygen atoms are present in 2.00 moles of $$\mathrm{CO_2$}$$?

Accepted Answer

$$2.41 	imes 10$$^{24}$$ atoms

Question 19

Which of the following is the correct name for $$\mathrm{K_2SO_3}$$?

Accepted Answer

Potassium sulfite

Question 20

A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{CH_2O}$$

Fundamental Concepts in General Chemistry: Matter, Measurement, and Nomenclature

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