Question

Please please help!

What is the mass percent of potassium chloride when 9.35 grams of potassium chloride is mixed into 162.98 grams of water? Choose the answer with the appropriate significant figures and choose the correct unit.

Answer 1

The mass percent of potassium chloride is 1.386%

calculation

mass percent = actual mass/ Theoretical mass x 100

Actual mass = 9.35 g

Theoretical mass is calculated as below

Step 1 : write the equation for reaction

KCl + H₂O → KOH + HCl

Step 2: find the moles of H₂O

moles = mass÷ molar mass

The molar mass of H₂O = (2 x1 ) +(16) = 18 g/mol

moles is therefore = 162.98 g÷ 18 g/mol =9.054 moles

Step 3: use the mole ratio to determine the moles of KCl

KCl: H₂O is 1:1 therefore the moles of KCl is also = 9.054 moles

Step 4: find the theoretical mass of KCl

mass = moles x molar mass

from periodic table the molar mass of KCl = 39 +35.5 =74.5 g/mol

mass = 9.054 moles x 74.5 g/mol =674.5 g

Theoretical mass is therefore = 9.35 g/ 674.5 g x 100 = 1.386%