Question

We need a 3.0M aqueous HCl solution to dissolve the middle of a penny which is made of nickel. What mass of HCl is contained in 2.40 L of a 3.0M solution?

Answer 1

Answer:

262.44 grams of HCl is contained in 2.40 L of a 3.0 M solution.

Explanation:

Molarity (M) or Molar Concentration is the number of moles of solute that are dissolved in a certain volume.

Molarity is calculated as the number of moles divided by the volume of the solution:

$Molarity=\frac{number of moles of solute}{volume of solution}$

Molarity is expressed in units $\frac{moles}{liter}$.

In this case:

• Molarity= 3 M
• Number of moles of solute= ?
• Volume of solution= 2.4 L

Replacing:

$3 M=\frac{number of moles of solute}{2.40 L}$

and solving you get:

number of moles of solute= 3 M* 2.40 L

number of moles of solute= 7.2 moles

Being the molar mass of HCl 36.45 g/mole, then you can apply the following rule of three: if 1 mole has 36.45 grams, 7.2 moles how much mass does it have?

$mass of HCl=\frac{7.2 moles*36.45 grams}{1 mole}$

mass of HCl= 262.44 grams

262.44 grams of HCl is contained in 2.40 L of a 3.0 M solution.

Answer 2

Answer:

262.8 g

Explanation:

Molarity = 3.0M

Mass = ?

Volume = 2.40L

The relationship between these quantities is given as;

Molarity = Number of moles / Volume

Number of moles =  Molarity * Volume

Number of moles = 3 * 2.4 = 7.2 mol

Mass = Number of moles * Molar mass

Molar mass of HCl = 1 + 35.5 = 36.5 g/mol

Mass = 7.2 *   36.5 = 262.8 g