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Molarity. Molality. Normality

1. Let say we have 100 ml of H2SO4 solution and it contains 0.49 g of H2SO4

What is Molarity?

What is Molality?

What is Normality?

1 Molar solution contains a number of grams equal to molecular mass per one liter of solution.

MW of H2SO4 = 2 +32 +4* 16 = 98g

I mole = 98g/L

We have to find how many grams of H2SO4 given solution are contained in 1 liter.

100 ml = 0.1 L and contains 0.49 g

1 L contains X g

X = 0.49 * 1 / 0.1 = 4.9 g.

98g/L – 1 mole

4.9 g/L – X moles

X = 4.9 * 1 / 98 = 0.05 moles

The molarity of a 100 ml solution of H2SO4, which contains 0.49 g of H2SO4, equals 0.05 moles.

What is Molality? Molality is moles of solute / kg of solvent.

A solute is a substance dissolved in another substance.

A solvent is a substance in which another substance is dissolved

What is normality? An equivalent is the molecular mass or mass of acid or base that produce one mole of protons (H+) or one mole of hydroxyl

(OH-) ions.

One mole of H2SO4 produces 2 moles of H+ then equivalent to H2SO4 = MW/2 = 49g/L

49g/L is 1 Normal solution

4.9g/L solution is – X N

X= 4.9 * 1/ 49 = 0.10 N.

The normality of 100 ml solution of H2SO4, which contains 0.49 g of H2SO4, equals 0.10 N.

2. We have 10 ml of NaOH unknown concentration. The solution was titrated with 0.10 N solution of H2SO4 and 15 ml were required for neutralization. What is the concentration of NaOH?

Nb * Vb = Na * Va

where V is volume, N is Normality, b – base and a – acid

Nb = Na * Va / Vb = 0.10 * 15 / 10 = 0.15 N

The concentration of NaOH = 0.15 N.

Weight and Volume problems:

1. How many liters of Hydrogen are produced from one liter of water?

2H20 = 2H2 +02

First, we have to find how many grams of water are spent and how many grams of H2 are produced?

MW of H20 = 2 +16 = 18

If we spent 2 molecules of H20 then we spent 18 * 2 =36 g.

MW H2 = 2 and we got 2 molecules of H2. 2*2 = 4g

36 g of water produces 4 g of Hydrogen

1000 g of water produces X g of Hydrogen.

X = 4 * 100 / 36 = 111.1 g

I mole of Gas under normal conditions occupies 22.4 liters.

So we have to know how many moles of H2 are produced.

1 mole of H2 equals 2 g

X mole of H2 equals 111.1g

X = 111.1g / 2g = 50.6 moles of H2

1 mole of H2 occupies 22.4 liters

50.6 moles of H2 occupy X liters

X = 50.6 moles * 22.4L = 1232 L