a 100 cm3 solution of sodium carbonate is prepared by dissolving 8.653 g of the salt in water . the density of solution is 1.0816 g per mililitre . what are the molality and molarity of the solution?
Answers
Answer:
Explanation:
Molality = Moles of solute / Kilograms of solvent.
Molar mass of Sodium Carbonate :
= 23 × 2 + 12 + 16 × 3 = 106
Moles of the solute = 8.653/106 = 0.081632 moles
0.081632 moles — 100 cm³
? —1000 cm³
1000/100 × 0.081632 = 0.81632 moles per liter
Mass of the solvent = volume of solvent × density
= 100 × 1.0816 = 108.16 g
108.16/1000 = 0.10816 kg
Molality = 0.081362/0.10816
= 0.7224 moles per kilogram of solvent.
Molarity = 0.81632 moles per liter.
Answer:
Molarity: 0.816M
Molality:0.820m
Explanation:
THE DATA GIVEN:
In the question we are given the mass of Sodium carbonate:8.653 g
It is also stated that it is dissolved in water and 100 cc of Sodium Carbonate
is obtained as the product.
Density of SOLUTION FORMED IS 1.0816 g/ml
SOLUTION:
First we will find the number of moles of the reactant:
The Molecular mass of Na2CO3=106 g/mole
So no of moles= given mass/Molecular mass
Which is 8.653/106=0.0816 moles.
As we know the moles, and we have the volume of solution therefore we can find out the MOLARITY::
Molarity=moles/Volume of solution in litres
Now 1 cc=1/1000 litres
So MOLARITY= (0.0816*1000)/100= 0.816M
NOW FOR MOLALITY:
We are given the density of solution as 1.0816 g/ml and we know the volume (100 ml)
We can find mass:
Mass=Volume X Density
Therefore Mass of solution=108.16 g
We can now find the mass of solvent since we are given the mass of solute:
Mass of SOLVENT= Mass of SOLUTION - Mass of SOLUTE
Mass of SOLVENT= 108.16-8.653(data in question)
=99.507g=99.507/1000 kg
NOW MOLALITY=moles of solute/mass of SOLVENT in KG
THEREFORE
m=(0.0816*1000)/99.507
=0.820 m