How many grams are in 1 mole of carbon?

Use your Chemistry STAAR reference material to help you.

A. 6.02 × 10²³
Incorrect. This is Avogadro’s number. This is used to represent the amount of particles in a substance.

B. 6
Incorrect. This is the number of protons in carbon.

C. 12
Correct! This is the molar mass of carbon and therefore, the amount of grams present in 1 mole of carbon.

D. 18
Incorrect. This is not the number of grams in 1 mole of carbon.

How many atoms are in 2.00 moles of sodium?

Use your Chemistry STAAR reference material to help you.

A. 1.20 × 10²³
Incorrect. Check your calculation.

B. 3.32 × 10^-24
Incorrect. You divided the moles by Avogadro’s number. That is not the correct operation.

C. 4.6 × 10¹
Incorrect. This would be the number of grams present in 2 moles of sodium.

D. 1.20 × 10²⁴
Correct! This is the number of atoms in 2 moles of sodium.

2.41 × 10²⁴ particles = ____moles?

Use your Chemistry STAAR reference material to help you.

A. This value cannot be determined because the substance is unknown.
Incorrect. The number of moles can be determined when given the particles without knowing the substance.

B. 4.00
Correct!

C. 1.45 × 10⁴⁸
Incorrect. You multiplied the number of particles by Avogadro’s number. That is not the correct operation.

D. 4.0 × 10²³
Incorrect. Check your calculation.

Which of the following would you use to convert 120 grams of Ca to atoms of Ca?

Use your Chemistry STAAR reference material to help you.

A. 40.1 1 × 1 120 × 1 6.02 × 10²²
Incorrect. If you are converting 120 grams of Ca to atoms, the first equality should be 120 1 .

B. 120 1 × 40.1 1 × 6.02 × 10²³ 1
Incorrect. The second conversion factor should be flipped. You had 120 grams of Ca, and in order to cancel the grams you would need to have 40. One gram in the denominator and 1 mole in the numerator.

C. 120 1 × 1 40.1 × 1 6.02 × 10²³
Incorrect. The third conversion factor should be flipped. You need 1 mole in the denominator and 6.02 × 1023 in the numerator.

D. 120 1 × 1 40.1 × 6.02 × 10²³ 1
Correct! This would correctly convert 120 grams of Ca to atoms of Ca.