15.5g of potassium nitrate is dissolved in 200cm 3 of water. How many moles of potassium nitrate are presented in 15.5g of the compound?

1 Answer
Mar 2, 2018

"0.0075 mol" KNO_3

Explanation:

FIRST

Look for the Molar mass of KNO_3 = 101.10 g/mol

NEXT
Convert grams to moles:

(15.5 g)/(101.10 "g/"mol") = 0.1533 mol

Dissolved in 200 cc (0.2 L of water)

("0.1533 mol"/"0.2 L")

Assume Water density = 1 g/l

"Total weight of compound" = 15.5 + 200 = 315.5 g

Make the relation to find the moles of K:

("0.1533 mol of K are dissolved in"/"315.5 g of compound"")x("15 g of compound") =

"0.0075 mol" KNO_3