Question

A 14.3 g sample of HF is dissolved into 250 mL of solution. The concentration of the solution is *

Answer 1

Answer:

The concentration of the solution is 2.86 M

Explanation:

Molarity is a unit of concentration based on the volume of a solution. It is defined as the number of moles of solute that are dissolved in a given volume. In other words, molarity is defined as the number of moles of solute per liter of solution.

The Molarity of a solution is determined by the following expression:

$Molarity (M)=\frac{number of moles of solute}{Volume}$

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

In this case, you must then know the number of moles of HF, for which you must know the molar mass. Being:

• H: 1 g/mole
• F: 19 g/mole

the molar mass of HF is: HF= 1 g/mole + 19 g/mole= 20 g/mole

Then the following rule of three applies: if 20 g of HF are available in 1 mole, 14.3 g in how many moles will they be?

$moles=\frac{14.3 g*1 mole}{20 g}$

moles= 0.715

So:

• number of moles of solute: 0.715 moles
• Volume: 250 mL=0.250 L (being 1 L=1000 mL)

Replacing:

$Molarity=\frac{0.715 moles}{0.250 L}$

Solving:

Molarity= 2.86 $\frac{moler}{liter}$=2.86 M

The concentration of the solution is 2.86 M