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

$$\text{Molar Mass} = \frac{\text{mass}}{\text{amount of substance}}$$

Question 1

Which of the following best describes molar mass?

Accepted Answer

The mass of one mole of a substance, expressed in grams per mole ($$g/mol).$$

Question 2

Given the formula $$\mathrm{(NH_4$)_2SO_4}$$, what is the correct way to determine the number of hydrogen atoms present?

Accepted Answer

Multiply the subscript of $$\mathrm{NH_4$} by $$the subscript of H.

Question 3

What is the molar mass of $$\mathrm{C_6H_{12}O_6$} ($$glucose)? (Atomic masses: C = 12.01, H = 1.008, O = 16.00)

Accepted Answer

$$180.16\ g/mol$$

Question 4

A chemist needs to prepare 10.0 g of $$\mathrm{(NH_4$)_2SO_4}. $$How many moles does this represent? (Molar mass = $$132.14\ g/mol)$$

Accepted Answer

$$0.076$$ moles

Question 5

Which step is NOT part of the process for calculating the molar mass of a compound?

Accepted Answer

Dividing the total mass by Avogadro's number.

Question 6

Calculate the molar mass of $$\mathrm{Ca(H_2PO_4)_2}. ($$Atomic masses: Ca = 40.08, H = 1.008, P = 30.97, O = 16.00)

Accepted Answer

$$234.10\ g/mol$$

Question 7

A sample of diazepam (Valium) has a mass of $$15.86\ g. If $$its molar mass is $$284.74\ g/mol$$, how many moles are present?

Accepted Answer

$$0.0557$$ moles

Question 8

Which of the following compounds contains the greatest number of oxygen atoms per formula unit?

Accepted Answer

$$\mathrm{Fe(NO_3$)_3 \cdot 9H_2O}$$

Question 9

A hydrate of nickel(II) chloride, $$\mathrm{$$NiCl_2$$ \cdot 6H_2O}$$, is used in a laboratory. What is the correct way to calculate its molar mass?

Accepted Answer

Add the molar mass of $$\mathrm{$$NiCl_2$$} to $$six times the molar mass of $$\mathrm{H_2O}.$$

Question 10

If you have 5.00 g of $$\mathrm{Fe(NO_3$)_3 \cdot 9H_2O} ($$molar mass $$404.00\ g/mol$$), how many moles do you have?

Accepted Answer

$$0.0124$$ moles

Question 11

Which of the following is the correct formula for calculating molar mass?

Accepted Answer

$$	ext{Molar Mass} = \frac{	ext{mass}}{	ext{amount of substance}}$$

Question 12

A student calculates the molar mass of $$\mathrm{Ca(H_2PO_4)_2} as$$ $$234.10\ g/mol. If $$they have $$46.82\ g of $$the compound, how many moles do they have?

Accepted Answer

$$0.200$$ moles

Question 13

Which of the following best explains why hydrates have higher molar masses than their anhydrous forms?

Accepted Answer

Hydrates include additional water molecules in their structure.

Question 14

A compound contains 2 moles of nitrogen, 8 moles of hydrogen, 1 mole of sulfur, and 4 moles of oxygen per formula unit. Which compound is this?

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Calculating Molar Mass: Concepts and Practice

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