Question

A solution is made from ethanol, C2H5OH and water is 0.75 m. How many grams of ethanol are contained per 250. g of water?
A

Answer 1

Answer:

$m_{solute}=8.6g$

Explanation:

Hello,

In this case, the unit of concentration is molality which is defined by:

$m=\frac{n_{solute}}{m_{solvent}}$

Whereas the mass of the solvent is measured in kilograms. In such a way, with the given data, we first compute the kilograms of water:

$m_{solvent}=250g*\frac{1kg}{1000g} =0.25kg$

Then, we solve for the moles of the solute:

$n_{solute}=0.75\frac{mol}{kg}*0.25kg =0.19mol$

Finally since the molar mass of ethanol is 46 g/mol, we compute the grams for the given solution:

$m_{solute}=0.19*\frac{46g}{1mol} \\\\m_{solute}=8.6g$

Best regards.