Question

Solution stoichiometry allows chemists to determine the volume of reactants or products involved in a chemical reaction when the chemical substances are dissolved in water. Instead of using mass to calculate the resulting amount of reactants or products, molarity and volume will be used to calculate the moles of substances. A 20.00 mL sample of a 0.250 M solution of HCl reacts with excess Ba(OH)2. What mass of H2O is produced in the reaction?

Answer 1

Answer:

90 mg of H₂O

Explanation:

The reaction that takes place is:

2HCl + Ba(OH)₂ → BaCl₂(aq) + 2H₂O

With the information given by the problem and the definition of molarity (M=n/V), we can calculate the moles of HCl:

20.00 mL * 0.250 M = 5 mmol HCl

Now we use the stoichiometric ratio to convert moles of HCl to moles of H₂O and then to mass of H₂O:

5 mmol HCl * $\frac{2mmolH_{2}O}{2mmolHCl} *\frac{18mg}{1mmolH_{2}O}$ = 90 mg H₂O