Lab Experiment:
Question 1. Determine the molar mass of an unknown acid. Called the unknown acid HX, and it reacts with NaOH. Equation is:
NaOH(aq)+HX(aq)→NaX(aq)+H2O(l)
1 mole of NaOH reacts with 1 mole of HX.
Weighed a sample of HX is titrated with standard NaOH.
Weigh the vial containing the acid unknown = 6.9932g
Removed approx 0.5g of the HX sample from the vial to a beaker.
Weighed the vial again = 6.5180g
Now I know the exact weight of the HX sample.
First I will add 10mL of water to the sample to dissolve it completely along with a few drops of an acid base indicator.
Prepared a standard titrant solution. In this example, the titrant concentration is 0.09156mol/L NaOH solution.
31.90mL of the titrant was poured into the solution until the solution was able to change color.
With these results, what is the molar mass of this sample?
Question 2. Analysis of calcium carbonate content of using a back nitration.
Equation is:
CaCO3(aq)+2HCl(aq)→CO2(g)+H2O(l)+CaCl2(aq)
The CaCO3 is dissolved in HCl. Note that the dissolution of the CaCO3 in HCl is a chemical reaction. In order to be surethat all the CaCO3 dissolves an excess of HCl is deliberately added.
Next step involves the titration of the excess HCl using a standard NaOH solution.
HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l)
Our sample consists of a fine white powder contained in a vial.
Weigh the vial containing the sample=6.7799g
Removed approx 0.25g of the white powder sample from the vial to a beaker.
Weighed the vial again = 6.5247g
Now I know the exact weight of the whit powder sample.
First I will add 50mL of 0.1007 mol/L HCl delivered by a pipette to the sample to dissolve it completely along with a few drops of an acid base indicator.
Prepared a standard titrant solution. In this example, the titrant concentration is 0.02510mol/L NaOH solution.
41.40mL of the titrant was poured into the solution until the solution was able to change color.
With these results, what is the percentage of calcium carbonate in this sample?