Question

Prepare m/20 solution of oxalic acid

Answer 1

We have to prepare the standard solution of oxalic acid [ 250ml / 0.05 M] 

molar weight of oxalic acid $H_2(C_2O_4).2H_2O$  = 1 × 2 + 2 × 12 + 4 × 16 + 2(1 × 2 + 16) = 2 + 24 + 64 + 36 = 126g/mol 
mole = molarity × volume/1000 
= 0.05 × 250/1000 = 0.05/4 
mass of $H_2(C_2O_4).2H_2O$  = 0.05/4 × 126 = 1.575 g 

Use an electronic balance, we will weigh about 3.15 g of $H_2(C_2O_4).2H_2O$ crystals in a weighing bottle and transfer these into a 250ml beaker. 

wash the bottle two - three times, using distilled water and transfer all the washings into the beaker. Dissolve $H_2(C_2O_4).2H_2O$  crystals in the beaker by gentle stirring with a clean glass rod.

when $H_2(C_2O_4).2H_2O$ crystals dissolve completely in the beaker, transfer entire solution into 250ml standard flask through a funnel , using a glass rod. 

wash the beaker two to three times with distilled water and transfer all the washings into the standard flask and finally wash the funnel thoroughly with distilled water.  This transfers the solution completely into the standard flask.

now use a wash bottle, add enough distilled water to the standard flask so that the level is just below the calibration mark on it. Add the last few drops of distilled water with a pipette until the lower level of the meniscus just touches the mark on the standard flask.

stopper the measuring flask and shake gently to make the solution uniform throughout.

Answer 2

m/20 solution of oxalic acid can be prepared two steps.

Explanation:

Step 1:

Determine the mass of Oxalic acid.

Molar weight of oxalic acid = 126g/mol  

Number of moles = molarity × volume / 1000  

= 0.05 × 250 / 1000 = 0.05 / 4  

Mass of  Oxalic acid = moles x molecular weight = 0.0125 × 126 = 1.575 g  

Step 2:

• Now take a measuring flask and transfer 3.15 g of oxalic acid into it.
• Now add distilled water into the flask and dissolve the Oxalic acid into 50 ml water.
• Keep adding the water until the level of water touches the mark.
• m/20 solution of Oxalic acid will be ready.