1.

25 g of a solute of molar mass 250 g mol^(-1) is dissolved in 100 ml of water to obtain a solution whose density is 1.25 g ml^(-1). The molarity and molality of the solution are respectively

Answer»

0.75 and 1
0.8 and 1
1 and 0.8
1 and 0.75

SOLUTION :No. of moles of solute `=(25)/(250)=0.1` moles
Molarity `=("No. of moles of solute")/("Volume of solvent in litre")=(0.1)/((100)/(1000))=1M`
Molality `=("no. of moles of solute")/("mass of solvent in KG")`
Mass `= d xx V`
`=1.25xx100=125 g`
Molality `=(0.1)/(125//1000)=0.8m`.


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