Question

If a 66.5 g sample of ammonium nitrate (NH4NO3) is dissolved in enough water to make 315 mL of solution, what will be the molarity (M)?

Answer 1

Answer:

2.64 M

Explanation:

To find the molarity, you need to (1) convert grams to moles (via molar mass), then (2) convert mL to L, and then (3) calculate the molarity (via molarity ratio). The final answer should have 3 sig figs to match the sigs figs of the given values.

(Step 1)

Molar Mass (NH₄NO₃): 2(14.007 g/mol) + 4(1.008 g/mol) + 3(15.998 g/mol)

Molar Mass (NH₄NO₃): 80.04 g/mol

66.5 grams NH₄NO₃                1 mole
---------------------------------  x  ----------------------  =  0.831 moles NH₄NO₃
                                             80.04 grams

(Step 2)

1,000 mL = 1 L

 315 mL                1 L
--------------  x  ------------------  =  0.315 L
                        1,000 mL

(Step 3)

Molarity = moles / volume

Molarity = 0.831 moles / 0.315 L

Molarity = 2.64 M