Q: A solution is prepared by dissolving 27.5 g of ethanol in 175 g of water. What is the mass percent of ethanol in the solution?

$$\frac{27.5}{27.5 + 175} \times 100\% = 13.6\%$$

Q: What is the molar mass of water ($$H_2O$$)? (Atomic masses: H = 1.01 g/mol, O = 16.00 g/mol)

$$2 \times 1.01 + 16.00 = 18.02\ \text{g/mol}$$

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

$$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$$

Q: A compound contains 24.5% carbon by mass. If you have 100 g of the compound, how many moles of carbon are present? (Atomic mass of C = 12.01 g/mol)

$$\frac{24.5\ \text{g}}{12.01\ \text{g/mol}} = 2.00\ \text{mol}$$

Q: What is the correct formula for percent error?

$$\frac{\text{experimental value} - \text{actual value}}{\text{actual value}} \times 100\%$$

Q: Which of the following is the correct formula for molarity?

$$M = \frac{\text{moles of solute}}{\text{liters of solution}}$$

Question 1

Which of the following statements best describes the Law of Conservation of Mass as it applies to a chemical reaction?

Accepted Answer

Matter is neither created nor destroyed during a chemical reaction.

Question 2

A student measures the mass of a sample as 18.975 g. According to proper reporting of measurements, which digit is estimated?

Accepted Answer

The digit '5' in 18.975

Question 3

Which of the following is the correct scientific notation for the number 0.000124?

Accepted Answer

$$1.24 	imes 10$$^{-4}$$

Question 4

A solution is prepared by dissolving 27.5 g of ethanol in 175 g of water. What is the mass percent of ethanol in the solution?

Accepted Answer

$$\frac{27.5}{27.5 + 175} 	imes 100\% = 13.6\%$$

Question 5

Which separation technique would be most appropriate for separating sand from water?

Accepted Answer

Filtration

Question 6

What is the molar mass of water ($$H_2O$$)? (Atomic masses: H = 1.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$$2 	imes 1.01 + 16.00 = 18.02\ 	ext{g/mol}$$

Question 7

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

Accepted Answer

$$	ext{Density} = \frac{	ext{Mass}}{	ext{Volume}}$$

Question 8

A compound contains 24.5% carbon by mass. If you have 100 g of the compound, how many moles of carbon are present? (Atomic mass of C = 12.01 g/mol)

Accepted Answer

$$\frac{24.5\ 	ext{g}}{12.01\ 	ext{g/mol}} = 2.00\ 	ext{mol}$$

Question 9

Which scientist is credited with the discovery of the electron using the cathode ray tube experiment?

Accepted Answer

J.J. Thompson

Question 10

What is the correct formula for converting Celsius to Kelvin?

Accepted Answer

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

Question 11

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 12

A 6.00 M $$K_2SO_4$$ solution is prepared. What is the concentration of $$K^+$$ ions in the solution?

Accepted Answer

$$12.00\ 	ext{M}$$

Question 13

Which of the following is the correct empirical formula for a compound with 40% C, 6.7% H, and 53.3% O by mass? (Atomic masses: C = 12.01, H = 1.01, O = 16.00)

Accepted Answer

$$CH_2O$$

Question 14

Which of the following is NOT a property of a solid in terms of particle arrangement?

Accepted Answer

Particles are separated by long distances

Question 15

What is the correct formula for percent error?

Accepted Answer

$$\frac{	ext{experimental value} - 	ext{actual value}}{	ext{actual value}} 	imes 100\%$$

Question 16

Which of the following is the correct representation for the isotope of carbon with a mass number of 14?

Accepted Answer

$$^{14}_{6}C$$

Question 17

Which of the following is a correct statement about ions?

Accepted Answer

Cations are positively charged ions formed by losing electrons.

Question 18

Which of the following is the correct formula for molarity?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}$$

Question 19

Which of the following best describes a chemical change?

Accepted Answer

A process where the chemical composition of the original substance is changed.

General Chemistry Foundations: Matter, Atoms, Molecules, and Solutions

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