Fig. 1 shows a car battery technician measuring the pH of a spill after it has been diluted with water. The battery contains sulfuric acid. The technician m...
Question 1 Report
Fig. 1 shows a car battery technician measuring the pH of a spill after it has been diluted with water. The battery contains sulfuric acid. The technician must decide whether sodium hydrogencarbonate powder can be used to make the spill safer.
(a) Name the ion responsible for the acidic properties of the spill. [1]
(b) Describe what happens to pH when sodium hydrogencarbonate neutralises the acid. [1]
(c) Explain why water should be added slowly to a concentrated acid spill. [2]
This solution is prepared by a student who needs 1000 cm3 of dilute hydrochloric acid for a reaction-rate investigation. Fig. 1 shows concentrated acid being transferred into a measuring cylinder already containing water. The student must use the correct order of mixing.
(a) Name the piece of equipment used to measure 1000 cm3 accurately in a laboratory. [1]
(b) Describe the correct order for mixing acid and water. [1]
(c) Explain why acid is added to water rather than water to acid. [2]
Answer Details
Safe dilution and neutralisation
For the battery spill: (a) The ion responsible for acidic properties is the hydrogen ion, \(\mathrm{H^+}\). [1] (b) As sodium hydrogencarbonate neutralises the acid, pH increases towards 7. [1] (c) Dilution can release heat. Adding water slowly reduces rapid heating and splashing. [2]
For preparing dilute acid: (a) A measuring cylinder or volumetric flask can measure 1000 cm3 accurately. [1] (b) Add acid slowly to water. [1] (c) Mixing releases heat. The larger amount of water absorbs the heat, reducing boiling and dangerous acid splashes. [2]
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