The document explains various concepts in chemistry, focusing on calculations of molarity, molality, normality, mass percentage, volume percentage, and mole fraction using specific examples. It provides step-by-step solutions to problems related to these concepts, demonstrating how to derive concentrations and percentages based on given quantities. Each section includes examples with clear formulas for performing the calculations.

1. NME chemistry
By:
R.Vaishnavi
II Msc Mathematics

2. Problems
A.Molarity:
1. What is the molarity of a 250 ml solution
containing 0.35 moles Nacl?
Soln:
first we convert ml to l,
250ml(1L/1000ml) = 0.25L
Formula:
M = Molarity = Moles of soute
Litres of solution

3. 0.35 mole Nacl
̿ 0.25 L solution
= 1.4 M Nacl
2. Suppose we have 35 ml of a 0.85M Mgcl2 solution.
How many moles of Mgcl2 are present in the
solution?
soln:
first we convert ml to l
35ml(1L/1000ml) = 0.035L
Using the formula of molarity,
M = Molarity Moles of solute
̿ Literes of solution
Mole of solute = Molarity*Literes of solution

4. = (0.035L)*(0.85mole)
= 0.030 mol Mgcl2
B. Molality:
1. Calculate the molality ofan antifreeze solution
made by dissolving 186g of antifreeze (c2 H6 O2 )
in 2Kgofwater?
soln:
first we convert grams to moles,
=186g c2 H6 O2 /62.07g c2 H6 O2
= 2.99 = 3 mol c2 H6 O2

5. m = Molality Moles of solute
̿ Kg of solvent
m = 3 mole/2Kg
= 2 m c2 H6 O2
2. What is the molality of a solution in which 2.75
moles of Nacl are dissolved in 1.25Kg of water?
soln:
Given, moles of solute = 2.75 mole Nacl
mass of solvent = 1.25 Kg water
To find,Molality (m) of solution,
m = Molality Moles of solute
̿ Kg of solvent

6. = (2.75 mole Nacl)/(1.25 of water)
= 2.2 m Nacl
C. Normality:
1.Find the normality of H2So4 having 49g H2So4 present in
500ml of solution?
soln:
first we convert ml to L,
500ml = (500/1000)L
= ½ L
Using the normality formula,
N = Normality
= (Equaivalent of solute)/(litere of solution)

7. = 49g/(92/2)*(500/1000L)
= 49g/46*(1/2)L
= 2.13 N
2. Calculate the normality of NaoH having 2g is
present in 800ml solution?
soln:
first we convert ml to L,
800ml = (800/1000L) = (8/10)L
N= 2g/(40/1)*(0.8)
= 0.06 N

8. D. Mass percentage:
1. If 28.5g of calcium hydroxide Ca(OH)2 is dissolved
in enough to make 185g of solution, What is the
percent by mass of Ca(OH)2 in the solution?
soln:
Given,
Mass of solute = 28.5g,
Mass of solution = 185g
Mass% = (Mass of solute/Mass of solution)*100
= (28.5g/185g)*100
= 15.4%

9. 2. What is the mass % of Na2so4 in a solution made
by dissolving 25.g Na2so4 in 225.0g H2O?
soln:
Given,
Mass of solute = 25.0g Na2so4
Mass of solvent = 225.0 H2O
Using the Mass% formula,
Mass% = (25.0g Na2so4)/(225.0gH2O+25.0
Na2so4)

10. = 25.0/250.0
= 10%
E. Volume percentage:
1. A solution is made from 35ml of methanol and 65ml of
water. Calculate the volume percentage?
soln:
Given,
Volume of methanol = 35ml
Volume of water(solvent) = 65ml
Using the volume percentage,
= ((Volume of the solute/Volume of the
solution)*100

11. =[Volume of the solute/(Volume of the solute+Volume of the
solvent)]*100
= [35/(35+65)]*100
= (35/100)*100
= 35%
2. Calculate the volume of ethanol in 200ml solution of 20% v/v
aqueous solution of ethanol?
soln:
Given, Volume of aqueous solution = 200ml
Volume% = 20%
Using the formula of volume percentage,
20 = [Volume of ethanol(solute)/200]*100
Volume of ethanol = (20*200)/100 = 40ml

12. F. Mole Fraction:
1. Calculate the mole fraction of Mgcl2 and H2O, if 2 moles of Mgcl2
are dissolved in 100 grams of water?
soln:
Given, the number of mole of MgCl2 = A = 2 mole
The molecular weight of H2O = 18 gram per mole
Number of moles of H2O = B = (Given weight/Molecular weight)
B = 55.6 moles
Using the mole fraction formula,
Mole fraction of MgCl2 = Number of moles of MgCl2/Total moles
= A/(A+B) = 2/57.5 = 0.034

13. Mole fraction of H2O = B/(A+B)
= 55.6/57.6
= 0.96
2. Calculate the mole fraction of Ethanol and water, if 3 moles of
ethanol are dissolved in 1000 grams of water?
Soln:
The molecular weight of H2O = 18 gram per mole
Number of moles of H2O = A = Given weight /Molecular weight
= 55.6 moles
Number of moles of ethanol = B = 3 moles
Moles fraction of ethanol = B/(A+B) = 3/58.6
= 0.05119

14. Mole fraction of H2O = A/(A+B)
= 55.6/58.6
= 0.9488

15. Thank you