Question

Indicate the appropriate protocol below to prepare the required solution

A) Solution 1 Preparation: Prepare: 1 liter of 2 Molar Tris From: solid Tris, MW = 121.1 g/mol Procedure:

B) Solution 2 Preparation: Prepare: 1 liter of 0.01 mg/mL ascorbic acid From: solid ascorbic acid , MW = 176.1 g/mol Procedure:

C) Solution 3 Preparation: Prepare: 1 liter of 100 mM Tris From: 1 Molar Tris stock solution Procedure:

D) Solution 4 Preparation: Prepare: 1 liter of 50 mM CaCl2 From: 1 Molar CaCl2 Procedure:

E) Solution 5 Preparation: Prepare: 100 mL of 23% mannitol From: solid mannitol Procedure:

Answer 1

If we have a stock solution of certain molarity, to prepare a working concentration, the formula to be used is –

V₁S₁ = V₂S₂, V=volume, S=strength

There are two sides in the above equation, one side corresponds to the stock concentration and the other to the working concentration. You are free to choose any one of the two sides for stock, just choose the other one for working concentration. I am choosing the left side (V₁S1) for working concentration.

Preparing a solution of a particular molarity from solid solute –

1Molar solution – Weigh the amount of the solute that amounts to the molecular weight in gram, add water to it to make the volume up to 1000ml.

Answers -

A) Solution 1 - 1 liter of 2 Molar Tris From: solid Tris, MW = 121.1 g/mol

Procedure:

You have to take 121.1g Tris for 1Molar. For 2 Molar, Weigh 242.2g of Tris, add water to make the volume up to 1 Liter.

B) Solution 2 - 1 liter of 0.01 mg/mL ascorbic acid from: solid ascorbic acid, MW = 176.1 g/mol

Procedure:

0.01mg/mL = 0.01mg in 1 mL, which is same as 10mg in 1000mL. Take 1L water, add 10mg of solid ascorbic acid.

C) Solution 3 - 1 liter of 100 mM Tris From: 1 Molar Tris stock solution

Procedure:

V₁ = 1Liter, S₁ = 100mM = 0.1M, V₂ = ?, S₂ = 1M

V₁S₁ = V₂S₂

=> 1 x 0.1 = V₂ x 1

=> V₂ = 0.1 Liter = 100mL

Take 100mL of the stock and add make the volume up to 1000mL with water.

D) Solution 4 - 1 liter of 50 mM CaCl2 From: 1 Molar CaCl2

Procedure:

V₁ = 1L, S₁ = 50mM = 0.05M, V₂ = ?, S₂ =1M

V₁S₁ = V₂S₂

=> 1 x 0.05 = V₂ x 1

=> V₂ = 0.05L = 50mL

Take 50mL of the stock and make the volume up to 1000mL with water.

E) Solution 5 - 100 mL of 23% mannitol from: solid mannitol

Procedure:

Weigh 23gm of mannitol, add water, and make the volume up to 100 mL