Question

A 17.0-g sample of hf is dissolved in water to give 2.0 x 10 2 ml of solution. the concentration of the solution is:

Answer 1

The concentration of the HF solution: M = 4.25 M

Step-by-step explanation:

Molarity, denoted by M, is the molar concentration of a given solution. It is the ratio of number of moles of solute and the total volume of the solution in L.

Molarity of a solution is given by,

`M = (Number\: of\: moles\: of \: solute\: (n))/(Total\: volume\: of\: the\: solution\: (V)(in\: L))`

and,
`n = (Given\: mass\: of\: solute\: (w))/(Molar\: mass\: of\: solute\: (m))`

Given: Total volume of solution: V = 2 × 10² mL = 2 × 10² × 10⁻³ L = 0.2 L (∵ 1 mL = 10⁻³ L)

Given mass of solute (HF): w = 17 g, Molar mass of solute (HF): m = 20 g/mol

Molarity of HF solution: M = ?

So the number of moles of solute (HF):

`n = (w)/(m) = (17\: g)/(20\: g/mol) = 0.85\: mol`

Therefore, the Molarity of the HF solution:

`M = (n)/(V(in\: L)) = (0.85\: mol)/(0.2\: L) = 4.25\: mol/L\: or\: 4.25\: M`

Therefore, the concentration of the HF solution: M = 4.25 M

Answer 2

The concentration of the solution is 4.25 M

Explanation

molarity=moles/volume in liters

moles = mass/molar mass
molar mass of HF = 19 + 1 = 20 g/mol
moles is therefore = 17.0 g/ 20 g/mol = 0.85 moles

volume in liters = 2 x10^2ml/1000 = 0.2 liters

therefore molarity = 0.85/0.2 = 4.25 M