Leaving Cert Chemistry - Standardising a Solution of Hydrochloric Acid with Sodium Carbonate Solution

Why is hydrochloric acid not used as a primary standard?
1. It is not obtained sufficiently pure.
2. Its volume cannot be accurately determined.
3. It is a very reactive substance.
4. It absorbs carbon dioxide from the surrounding air.
Which one of the following pieces of apparatus would you NOT use during this titration?
1. Liebig condenser
2. Burette
3. Pipette filler
4. Conical flask
In this experiment, a hydrochloric acid solution is standardised against a standard solution of sodium carbonate (Na₂CO₃). Which ONE of the following sets of properties makes sodium carbonate an ideal primary standard?
1. It is obtained pure, is very stable and easily dissolves in water.
2. It is obtained pure, is very stable and is colourless in solution.
3. It is very stable, has a low relative molecular mass and absorbs moisture from the surrounding air.
4. It is unreactive, easily dissolves in water and very stable.
Which one of the following equations is correct for the reaction between hydrochloric acid and sodium carbonate?
1. Na₂CO₃ + 2HCl ---> 2NaCl + H₂O + CO₂
2. Na₂CO₃ + HCl ---> NaCl + H₂O + CO₂
3. Na₂CO₃ + 2HCl ---> NaCl + H₂O
4. Na₂CO₃ + 2HCl ---> 2NaCl + CO₂
Before starting the titration, the pipette, burette and conical flask are rinsed with deionised water and NOT tap water. Why is this?
1. Tap water contains ions that may affect the titration result.
2. Ions in the tap water may 'clog up' the tap of the burette.
3. The acid, when placed in the burette will become more dilute if tap water rather than deionised water is used to rinse the burette.
4. The colour change at the end-point of the titration is more noticeable if deionised water is used.
Further rinsings of the glass apparatus are made. Which one of the following should you NOT do?
1. Rinse the funnel with deionised water.
2. Rinse the burette with hydrochloric acid.
3. Rinse the pipette with sodium carbonate solution.
4. Rinse the conical flask with sodium carbonate solution.
When placing the acid in the burette, which one of the following procedures is INCORRECT?
1. The top of the meniscus is read when doing the titration.
2. The burette is filled to the zero mark when filling it up.
3. Any air bubble below the tap is removed before the titration.
4. The funnel is removed from the top of the burette before the titration.
When pipetting the sodium carbonate solution into the conical flask, which one of the following procedures is always carried out?
1. A pipette filler is used instead of using one's mouth to suck up the solution.
2. The pipette is always rinsed with sodium carbonate solution first and then with deionised water.
3. When emptying the contents of the pipette into the conical flask, the last few drops are blown out.
4. The sodium carbonate solution must be pipetted directly from the volumetric flask into the conical flask.
Why is the sodium carbonate mixed with the acid in a conical flask rather than a beaker?
1. To prevent any of the solutions splashing out when swirling the flask.
2. The conical flask is more accurate for measuring volume.
3. Its easier to see the colour change in a conical flask.
4. The conical flask will be less likely to break during the titration.
When adding the indicator to the conical flask, only two or three drops are added because
(i) too much indicator may make it difficult to see the colour change at the end-point clearly,
(ii) the indicator is corrosive, and adding too much poses a greater risk,
(iii) the indicator may be a weak acid or base and may interfere with the titration result.
Which of the above statements is/are correct?
1. (iii) only
2. All of them
3. (ii) and (iii) only
4. (i) and (ii) only
During the titration, the inside of the conical flask was washed down with deionised water. Why?
1. To ensure that all of the acid reacts with all of the base.
2. To enable the volume of acid to be read correctly.
3. To wash away any impurities on the inside of the conical flask.
4. To make the colour change at the end-point more visible.
When filling the burette with the acid solution
(i) it is first filled to the zero mark using a funnel,
(ii) any air bubble under the tap is removed by opening the tap to allow the bubble and some liquid escape,
(iii) the funnel is removed before starting the titration.
Which of the above procedures is/are NOT necessary?
1. (i) only
2. (ii) only
3. (iii) only
4. (i) and (ii) only
When adding the acid from the burette into the conical flask
(i) the acid is initially added drop by drop,
(ii) the conical flask is swirled while adding the acid,
(iii) the conical flask is placed over a white tile or white sheet of paper,
(iv) the inside of the conical flask is washed down from time to time with deionised water.
Which of the above procedures is/are not carried out during the titration?
1. (i) only
2. (iv) only
3. (ii) and (iii) only
4. (i) and (iii) only
If the colour of the indicator at the end-point changes from yellow to peach/pink, then which one of the following indicators was most likely to have been used?
1. methyl orange
2. phenolphthalein
3. litmus indicator
4. universal indicator
How many titrations should be carried out in order to give a valid result?
1. one rough titration and two accurate titrations that agree to within 0.1 cm³ of each other
2. one rough titration and one accurate titration
3. three titrations which are then averaged to get a result
4. two rough titrations and one accurate titration that agrees to within 0.5 cm³ of the rough titrations
Which one of the following formulae is the correct one for calculating the concentration of the acid solution?
What is the volume of acid in the burette shown?
1. 19.65 cm³
2. 20.15 cm³
3. 19.85 cm³
4. 19.6 cm³
If 25 cm³ of 0.1M sodium carbonate solution is used in this titration, how many moles of sodium carbonate is this?
1. 0.0025 mole
2. 2.5 moles
3. 0.005 mole
4. 0.5 mole
The equation for the reaction taking place in this titration is
Na₂CO₃ + 2HCl ---> 2NaCl + H₂O + CO₂
If A represents the acid, and B represents the base, then what are the values of N_A and N_B in calculating the concentration of the hydrochloric acid solution?
1. N_A = 2 and N_B = 1
2. N_A = 1 and N_B = 2
3. N_A = 2 and N_B = 2
4. N_A = 1 and N_B = 1
Using the correct values of N_A and N_B from the previous question, and given that 25 cm³ of 0.1 M sodium carbonate solution was used in neutralising 21 cm³ of hydrochloric acid solution, what is the concentration of the acid in moles per litre?
1. 0.24 mol/litre
2. 0.06 mol/litre
3. 0.024 mol/litre
4. 0.12 mol/litre
Given that the concentration of a hydrochloric acid solution is 0.24 mol/litre, what is this concentration in grams per litre? The molar mass of hydrochloric acid is 36.5 grams.
1. 8.76 grams/litre
2. 0.0066 grams/litre
3. 36.74 grams/litre
4. 8.52 grams/litre

Leaving Cert Chemistry - Standardising a Solution of Hydrochloric Acid with Sodium Carbonate Solution

Multiple Choice Quiz