Question

7. What is the molarity of the nitrate ion that is found in a solution made by dissolving 6.25g

of aluminum nitrate in a total volume of 325.0mL?

Answer 1

0.271 M NO₃⁻

Step-by-step explanation:

To find the molarity of the nitrate ion (NO₃⁻), you need to (1) convert grams to moles (via molar mass), then (2) convert moles Al(NO₃)₃ to moles NO₃⁻, then (3) convert mL to L, and then (4) calculate the molarity. When (Al(NO₃)₃) dissolves in water, it dissociates into 3 nitrate ions. The final answer should have 3 sig figs.

(Steps 1 + 2)

Molar Mass (Al(NO₃)₃): 26.982 g/mol + 3(14.007 g/mol) + 9(15.998 g/mol)

Molar Mass (Al(NO₃)₃): 212.985 g/mol

1 Al(NO₃)₃ = 1 Al³⁺ and 3 NO₃⁻

6.25 g Al(NO₃)₃ 1 mole 3 moles NO₃⁻
------------------------- x ----------------- x ----------------------- = 0.0880 moles NO₃⁻
212.985 g 1 mole Al(NO₃)₃

(Steps 3 + 4)

325.0 mL / 1,000 = 0.3250 L

Molarity = moles / volume

Molarity = 0.0880 moles / 0.3250 L

Molarity = 0.271 M