Question

Aqueous magnesium chloride solution is marketed as 20% by mass. Its density is 1.18 g/ml. Calculate (i) The mole fraction of each component(ii)Molarity (iii)Molality (iv) The concentration in ppm​

Answer 1

Explanation:

As you know, a 1.75-mol L−1

hydrochloric acid solution will contain

1.75

moles of hydrochloric acid, the solute, for every

1 L of solution.

So right from the start, you know that your solution must contain

1.75moles of hydrochloric acid.

Use the compound's molar mass to convert this to grams 1.75moles HCl.36.46 g

1

mole HCl=63.805 g

Now, you know that your stock solution is 36.0%

hydrochloric acid by mass, which implies that in order to have

36.0 g of hydrochloric acid, you need 100 g

of this solution.

You can thus say that in order for your target solution to contain

63.805 g

of hydrochloric acid, the sample you take from the stock solution must have a mass of

63.805g HCl⋅100 g solution36.0g HCl=

177.24 g

Use the density of the stock solution to figure out the volume of the sample

177.24g solution⋅1 mL

1.18g solution=

209 mL

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example hope