8 gm of caustic soda (molar mass 40) is dissolved in water and solutio

1.	8 gm of caustic soda (molar mass 40) is dissolved in water and solution is made to 800cm³. calculate the molarity of the solution
Answer» In the given question Solute = CAUSTIC soda Solvent = Water Number of moles of solute = Mass of solute ÷ Molar mass ⇒ Number of moles of solute = 8 ÷ 40 ⇒ Number of moles of solute = 0.2 moles We KNOW that 1 cm³ = 1 ML So, VOLUME of solution = 800 cm³ = 800 mL = 0.8 litres Molarity = Number of moles of solute ÷ Volume of solution ⇒ Molarity = 0.2 ÷ 0.8 ⇒ Molarity = 0.25 M ∴ Molarity of solution = 0.25 M REMEMBER: While FINDING out volume of solution note that it should always be in litres. Else multiply by 1000 Molarity is a temperature dependent term. Number of moles of solute should be solved and not of solvent.

8 gm of caustic soda (molar mass 40) is dissolved in water and solution is made to 800cm³. calculate the molarity of the solution

Answer»

In the given question

Number of moles of solute = Mass of solute ÷ Molar mass

⇒ Number of moles of solute = 8 ÷ 40

⇒ Number of moles of solute = 0.2 moles

We KNOW that

1 cm³ = 1 ML

So, VOLUME of solution = 800 cm³ = 800 mL = 0.8 litres

Molarity = Number of moles of solute ÷ Volume of solution

⇒ Molarity = 0.2 ÷ 0.8

⇒ Molarity = 0.25 M

∴ Molarity of solution = 0.25 M

REMEMBER:

While FINDING out volume of solution note that it should always be in litres. Else multiply by 1000
Molarity is a temperature dependent term.
Number of moles of solute should be solved and not of solvent.