Question

How many moles and numbers of ions of each type are present in the following aqueous solution? Enter your answers for the numbers of ions in scientific notation.

425 mL of a solution containing 6.73 × 10²² formula units of potassium bromide per liter

_____ mol potassium

_____ x 10 ____ ions potassium

______ mol bromide

_____ x 10 _____ ions bromide

Answer 1

Number of formula units of potassium bromide per liter = 6.73 × 10²²​ = (​6.73 × 10²²) / (6.023 x 10²³) = 0.1117 mol

1 L solution contains formula units of potassium bromide = 0.1117 mol

Hence, 0.425 L of a solution contains formula units of potassium bromide = 0.1117 x 0.425 = 0.0475 mol

So, 0.425 L of a solution contains potassium ions = 0.0475 mol

= 0.0475 x 10²³ ions potassium

0.425 L of a solution contains bromide ions = 0.0475 mol

= 0.0475 x 10²³ ions bromide