Question

Titrating to find the molar mass of an unknown acid.

Consider the effect of exposing the NaOH solution to the air.

a) Would the calculated molar mass be too high or too low if your standardized NaOH were exposed to air for a long period of time after the standardization? Explain how you reaced your conclusion.

b) Would the calculated molar mass be too high or too low if your NaOH solution were expsoed to the air for a long period of time before the starndardization? Explain how you reached your conclusion.

Answer 1

a) NaOH on exposure to  air, will react with the CO2 in air, to form Na2CO3 This means that NaOH as a solid or in solution will loose its strength with time and degree of exposure and solutions of NaOH will need to be standardised.

therefore the calculated molar mass will be too high if your standardized NaOH were exposed to air for a long period of time after the standardization

b) the calculated molar mass will be same ( not effected) if your NaOH solution were expsoed to the air for a long period of time before the starndardization

because  starndardization is being done so we will have correct value of the solution's molarity.