Q: Which of the following is the correct formula to convert a temperature of 68°F to Celsius?

$$\text{temp in } ^\circ\mathrm{C} = \frac{5}{9} (68 - 32)$$

Q: Which of the following is the correct value for Avogadro's number?

$$N_A = 6.022 \times 10$$^{23}$$

Q: A chemist needs to convert 2.50 miles to kilometers. Using the conversion factor $$1\ \mathrm{mi} = 1.609\ \mathrm{km}$$, what is the correct answer?

$$2.50\ \mathrm{mi} \times 1.609\ \mathrm{km/mi} = 4.02\ \mathrm{km}$$

Q: A sample of water is heated from 25°C to 75°C. If the specific heat of water is $$4.184\ \mathrm{J/g\ ^\circ C}$$, how much energy is required to heat 10.0 g of water?

$$q = m \times SH \times \Delta T = 10.0\ \mathrm{g} \times 4.184\ \mathrm{J/g\ ^\circ C} \times (75 - 25)\ ^\circ\mathrm{C} = 2092\ \mathrm{J}$$

Question 1

Which of the following best describes the difference between a compound and an element?

Accepted Answer

A compound can be broken down into simpler substances by chemical means, while an element cannot.

Question 2

A sample of a metal has a mass of 45.0 g and a volume of 15.0 mL. What is the density of the metal?

Accepted Answer

$$D = \frac{45.0\ \mathrm{g}}{15.0\ \mathrm{mL}} = 3.00\ \mathrm{g/mL}$$

Question 3

Which of the following is the correct formula to convert a temperature of 68°F to Celsius?

Accepted Answer

$$	ext{temp in } ^\circ\mathrm{C} = \frac{5}{9} (68 - 32)$$

Question 4

Which of the following statements about significant figures is correct?

Accepted Answer

Zeros between nonzero digits are always significant.

Question 5

A student measures the mass of a sample as 12.34 g and its volume as 6.0 mL. How many significant figures should the calculated density have?

Accepted Answer

2

Question 6

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A mixture in which the composition is not uniform throughout.

Question 7

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

Accepted Answer

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

Question 8

A chemist needs to convert 2.50 miles to kilometers. Using the conversion factor $$1\ \mathrm{mi} = 1.609\ \mathrm{km}$$, what is the correct answer?

Accepted Answer

$$2.50\ \mathrm{mi} 	imes 1.609\ \mathrm{km/mi} = 4.02\ \mathrm{km}$$

Question 9

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

Accepted Answer

Melting of ice to form liquid water.

Question 10

Which of the following best describes the Law of Conservation of Mass?

Accepted Answer

Mass is neither created nor destroyed in a chemical reaction.

Question 11

A sample of water is heated from 25°C to 75°C. If the specific heat of water is $$4.184\ \mathrm{J/g\ ^\circ C}$$, how much energy is required to heat 10.0 g of water?

Accepted Answer

$$q = m 	imes SH 	imes \Delta T = 10.0\ \mathrm{g} 	imes 4.184\ \mathrm{J/g\ ^\circ C} 	imes (75 - 25)\ ^\circ\mathrm{C} = 2092\ \mathrm{J}$$

Question 12

Which of the following is the correct definition of a hypothesis?

Accepted Answer

A tentative explanation for a set of observations that can be tested by experiments.

Question 13

Which of the following is a chemical property?

Accepted Answer

Iron reacts with oxygen to form rust.

Question 14

A student needs to prepare 250.0 mL of a solution. How many liters is this?

Accepted Answer

$$250.0\ \mathrm{mL} 	imes \frac{1\ \mathrm{L}}{1000\ \mathrm{mL}} = 0.2500\ \mathrm{L}$$

Question 15

Which of the following is the correct formula for calculating percent composition by mass of an element in a compound?

Accepted Answer

$$\%\ 	ext{composition} = \frac{	ext{mass of element}}{	ext{total mass of compound}} 	imes 100\%$$

Question 16

Which of the following is the correct way to express the molecular weight (MW) of a compound?

Accepted Answer

$$MW = \frac{	ext{grams}}{	ext{mole}}$$

Question 17

Which of the following is a correct example of a chemical change occurring in everyday life?

Accepted Answer

A silver spoon tarnishing when exposed to air.

Question 18

A student is asked to convert 5.00 feet to centimeters. Using the conversion factors $$1\ \mathrm{ft} = 12\ \mathrm{in}$$ and $$1\ \mathrm{in} = 2.54\ \mathrm{cm}$$, what is the correct answer?

Accepted Answer

$$5.00\ \mathrm{ft} 	imes \frac{12\ \mathrm{in}}{1\ \mathrm{ft}} 	imes \frac{2.54\ \mathrm{cm}}{1\ \mathrm{in}} = 152\ \mathrm{cm}$$

Question 19

Which of the following is the correct relationship for converting Kelvin to Celsius?

Accepted Answer

$$K = ^\circ\mathrm{C} + 273.15$$

General Chemistry 1007: Essential Concepts, Conversions, and Equations

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