A student performs a titration to determine the concentration of a solution of calcium hydroxide (Ca(OH)2\text{Ca(OH)}_2Ca(OH)2).
She uses this method:
State what the student should do while adding the acid, to make sure that the indicator changes colour permanently.
The table shows the student's titration results.
| Titration | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Volume of acid added in cm3\text{cm}^3cm3 | 18.90 | 18.15 | 18.35 | 18.25 |
Concordant results are volumes within 0.20 cm30.20\text{ cm}^30.20 cm3 of each other.
Identify which results are concordant.
Use the concordant results to calculate the average (mean) volume of acid added.
The table shows the titration results of another student.
| Parameter | Value |
|---|---|
| Volume of calcium hydroxide used in cm3\text{cm}^3cm3 | 20.0 |
| Concentration of nitric acid in mol/dm3\text{mol/dm}^3mol/dm3 | 0.0500 |
| Average volume of nitric acid added from burette in cm3\text{cm}^3cm3 | 16.40 |
The equation for the reaction is:
2HNO3+Ca(OH)2→Ca(NO3)2+2H2O 2\text{HNO}_3 + \text{Ca(OH)}_2 \rightarrow \text{Ca(NO}_3\text{)}_2 + 2\text{H}_2\text{O} 2HNO3+Ca(OH)2→Ca(NO3)2+2H2OCalculate the amount, in moles, of HNO3\text{HNO}_3HNO3 in 16.40 cm316.40\text{ cm}^316.40 cm3 of the nitric acid.
Calculate the amount, in moles, of Ca(OH)2\text{Ca(OH)}_2Ca(OH)2 in the calcium hydroxide solution.
Calculate the concentration, in mol/dm3\text{mol/dm}^3mol/dm3, of the calcium hydroxide solution.
Describe how you could use the method of crystallisation to obtain a pure, dry sample of calcium nitrate from a dilute solution of calcium nitrate.
