Q: A sample contains 3.0 moles of carbon atoms. How many atoms are present in the sample? (Avogadro's number $$= 6.022 \times 10$$^{23}$$)

$$1.81 \times 10$$^{24}$$ atoms

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

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

Q: A student needs to convert 98.6 $$^{\circ}F ($$normal human body temperature) to Celsius. Which formula should they use?

$$C = (F - 32) \times \frac{5}{9}$$

Q: Which of the following is the correct calculation for the average atomic mass of chlorine if $$^{35}Cl ($$mass = 34.969 amu, abundance = 75.77%) and $$^{37}Cl ($$mass = 36.966 amu, abundance = 24.23%) are present?

$$(0.7577 \times 34.969) + (0.2423 \times 36.966)$$

Question 1

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A mixture in which the individual components remain distinct, such as sand and iron filings.

Question 2

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

Accepted Answer

Melting of ice to form liquid water.

Question 3

A student measures the mass of a sample three times and records the values: 5.12 g, 5.13 g, and 5.11 g. The true value is 5.50 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 formula to convert a temperature from Celsius to Kelvin?

Accepted Answer

$$K = C + 273.15$$

Question 5

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 6

A sample contains 3.0 moles of carbon atoms. How many atoms are present in the sample? (Avogadro's number $$= 6.022 	imes 10$$^{23}$$)

Accepted Answer

$$1.81 	imes 10$$^{24}$$ atoms

Question 7

Which of the following is a chemical property?

Accepted Answer

Flammability of gasoline

Question 8

A compound contains only sodium and chlorine. Which of the following best describes this compound?

Accepted Answer

A pure substance

Question 9

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

Accepted Answer

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

Question 10

A student needs to convert 98.6 $$^{\circ}F ($$normal human body temperature) to Celsius. Which formula should they use?

Accepted Answer

$$C = (F - 32) 	imes \frac{5}{9}$$

Question 11

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

Accepted Answer

A compound is made of two or more elements chemically combined, while a mixture is a physical blend of substances.

Question 12

Which of the following is the correct calculation for the average atomic mass of chlorine if $$^{35}Cl ($$mass = 34.969 amu, abundance = 75.77%) and $$^{37}Cl ($$mass = 36.966 amu, abundance = 24.23%) are present?

Accepted Answer

$$(0.7577 	imes 34.969) + (0.2423 	imes 36.966)$$

Question 13

Which of the following is NOT a base SI unit?

Accepted Answer

Gram (g)

Question 14

A sample of gold has a mass of 96.5 g and a volume of 5.00 cm$$^3. $$What is the density of gold?

Accepted Answer

$$19.3\ 	ext{g/cm}^3$$

Question 15

Which of the following is a correct statement about the law of definite proportions?

Accepted Answer

A chemical compound always contains exactly the same proportion of elements by mass.

Question 16

Which of the following is the correct scientific notation for 0.000345?

Accepted Answer

$$3.45 	imes 10$$^{-4}$$

Question 17

Which of the following is a chemical change?

Accepted Answer

Burning wood in a fireplace

Question 18

A student records a measurement as 0.00450 m. How many significant figures does this measurement have?

Accepted Answer

3

Question 19

Which of the following is the correct formula to convert Fahrenheit to Celsius?

Accepted Answer

$$C = (F - 32) 	imes \frac{5}{9}$$

Question 20

Which of the following best describes the difference between mass and weight?

Accepted Answer

Mass is the amount of matter in an object, while weight is the force of gravity on that object.

General Chemistry 121: Matter, Measurement, and Atomic Structure

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