Answer to Question #185161 in General Chemistry for hayley samantha farah

Question

A concentrated solution of HCl has a molarity of 10.0 M. You add 23.50 mL to a flask and then dilute with water. The mass of the final solution is 125.0 g. What is the mass percent of HCl ?

Answer 1

Mass percent essentially means g of HCl/total grams of solution (x100%). So, in this problem we already know the total mass = 125.0 g. If we can find the mass of HCl, we can then easily solve for mass percent. To find mass of HCl, we will first find the moles of HCl and then convert to grams of HCl

10 M = 10 moles/L

10 moles/L x 0.02350 L = 0.2350 moles HCl used

Converting this to grams: 0.2350 moles HClx 36.5 g/mole = 8.578 g HCl present

mass percent = mass HCl/Total mass (x100%) = 8.578 g/125.0 g (x100%) = 6.86%