Question

Determine the mass of KI needed to create a 250. ml solution with a concentration of 2.25 M.

Answer 1

Explanation:

You can find the answer to this question by using the formula for molarity (M) to find the moles of KI, then converting moles to grams.

To do this you need to know:

The formula for molarity: M = mol/L

Unit conversions

How to convert from moles to grams

First, you need to convert 250. mL to L.

To do this you can either use the mnemonic, K(ing)H(enry)D(ied)B(y)D(rinking)C(hocolate)M(ilk) or by using the conversion factor (1 L / 1000 mL).

(Using the conversion factor) 250. mL × 1 L / 1000 mL = 0.250 L

Then, use the formula for molarity to find the moles of KI.

M = mol/L ⇒ 0.200 M = x mol / 0.250 L

(Solve for x) (0.250 L)(0.200 M) = x mol / 0.250 L (0.250 L)

x = 0.05 mol

Convert moles to grams of KI.

molar mass of KI: 165.97277 g

0.05 mol × 165.97277 g / 1 mol = 8.2986385 g KI ≅ 8.30 g KI