a 200 mL aqueous solution of ammonia has a concentration of 1.50 M. What mass of ammonia is dissolved in the solution?

Answer: 51 grams

Explanation:

Ammonia is a gas with a chemical formula of NH3.

Given that,

Amount of moles of NH3 (n) = ?

Volume of NH3 (v) = 200mL

since the standard unit of volume is liters, convert 200mL to liters

(If 1000mL = 1L

200mL = 200/1000 = 0.2L)

Concentration of NH3 (c) = 1.5M

Since concentration (c) is obtained by dividing the amount of solute dissolved by the volume of solvent, hence

c = n / v

Make n the subject formula

n = c x v

n = 1.50M x 0.2L

n = 3 moles

Now, calculate the mass of ammonia

Amount of moles of NH3 (n) = 3

Mass of NH3 in grams = ?

For molar mass of NH3, use the atomic masses:

N = 14g; H = 1g

NH3 = 14g + (1g x 3)

= 14g + 3g

= 17g/mol

Since, n = mass in grams / molar mass

3 moles = m / 17g/mol

m = 3 moles x 17g/mol

m = 51 grams

Thus, 51 grams of ammonia was dissolved in the solution.