Question

Calculate the number of moles of methanol in 5 litres of its 2m solution if the density of the solution is 0.981 kg/L.(Molar mass of methanol =32 gm mol-1)

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Answer 1

Answer:

9.2 mol

Explanation:

2moles of methnol means molar mass methnol used

2×32=64g

density=0.981kg/L refers there is 1kg of solvent

so, we have to add 64g+1kg that is 1000+64=1064g

total molar weight 1.064kg used

hence volume = M/d

v=1.064/0.981 gives us 1.085litre

so, 1.085L gives us 2 mole

than 5L gives us ?

5×2=10

10/1.085=9.22moles

Answer 2

Answer:

9.22 g

Explanation:

2 m solution of methanol means that 2 moles of methanol are dissolved in 1 kg (1000g) of water.

Mass of methanol in 2 moles= 2 X 32=64 g

Density of solution =0.981

total mass of sol.=mass of solute+mass of solvent.

=64g+ 1000g=1.064kg

Volume of solution=mass / volume

=1.064/0.984

=1.085

Now, 1.085 L of solution contain methanol =2mol

5.0L of solution contain methanol= 2. X 5

-----

1.085

=9.22 mol.