Question

How many grams of kbr must be dissolved to make 25.0 ml of a solution that has a molarity of 0.85 m?

Answer 1

Molarity is defined as the number of moles of solute in 1 L of solution 
molarity of solution to be prepared is 0.85 M
this means that there should be 0.85 mol of KBr in 1 L of solution 
if 1 L contains - 0.85 mol
then 25.0 mL should contain - 0.85 mol / 1000 mL x 25.0 mL = 0.0213 mol 
mass of KBr - 0.0213 mol x 119 g/mol = 2.53 g
mass of KBr that should be dissolved in 25.0 mL is 2.53 g