Question 1

Which equation correctly relates the mass of a substance to the number of moles using molar mass?

Accepted Answer

$$n = \frac{m}{M}$$

Question 2

A chemist has 36 grams of water ($$H_2O). $$What is the number of moles present? (Molar mass of $$H_2O = 18\ \mathrm{g/mol})$$

Accepted Answer

$$2$$ moles

Question 3

If you have 88 grams of $$CO_2$$, how many moles do you have? (Molar mass of $$CO_2 = 44$$\ \mathrm{g/mol}$$)

Accepted Answer

$$2$$ moles

Question 4

Which of the following best describes the use of molar mass in chemical calculations?

Accepted Answer

It allows conversion between the mass of a substance and the number of moles.

Question 5

A laboratory technician needs 0.25 moles of sodium chloride ($$NaCl) $$for an experiment. What mass of $$NaCl$$ should be weighed out? (Molar mass of $$NaCl = 58.5\ \mathrm{g/mol})$$

Accepted Answer

$$14.6\ \mathrm{g}$$

Question 6

Which step is necessary when converting from grams of a substance to moles?

Accepted Answer

Divide the mass by the molar mass.

Question 7

A patient is prescribed 0.1 moles of glucose ($$C_6H_{12}O_6$) for an IV solution. What mass of glucose should be used? (Molar mass of C_6H$$_{12}$$O_6 = 180$$\ \mathrm{g/mol}$$)

Accepted Answer

$$18\ \mathrm{g}$$

Question 8

Which of the following is a correct application of molar mass in a real-world scenario?

Accepted Answer

Calculating the amount of fertilizer needed for a specific number of moles of nitrogen.

Question 9

A reaction requires 0.5 moles of $$O_2. $$What is the mass of $$O_2$$ needed? (Molar mass of $$O_2 = 32$$\ \mathrm{g/mol}$$)

Accepted Answer

$$16\ \mathrm{g}$$

Question 10

A student has 24 grams of magnesium ($$Mg). $$How many moles of magnesium does the student have? (Molar mass of $$Mg = 24\ \mathrm{g/mol})$$

Accepted Answer

$$1$$ mole

Question 11

Which of the following best explains why molar mass is important in chemical reactions?

Accepted Answer

It allows chemists to measure out exact quantities of substances needed for reactions.

Question 12

A medication requires 0.05 moles of potassium iodide ($$KI). $$What mass of $$KI$$ should be used? (Molar mass of $$KI = 166\ \mathrm{g/mol})$$

Accepted Answer

$$8.3\ \mathrm{g}$$

Using Molar Mass in Chemical Calculations

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