You are planning an experiment to find how fast a carbonate reacts with dilute hydrochloric acid by collecting the gas given off. Fig. 1.1 shows the two mai...

This question tests recognition of standard gas-collection apparatus and how to assemble it so no gas leaks before it is measured. The reaction of a carbonate with hydrochloric acid, \( \text{carbonate} + \text{HCl} \rightarrow \text{salt} + \text{H}_2\text{O} + \text{CO}_2 \), gives off carbon dioxide, and the rate is found from how the gas volume grows with time.

(a) Naming the apparatus [2]. Piece A is the wide-based vessel that holds the reactants, a conical flask [1]. Piece B, the graduated barrel with a moving plunger, is a gas syringe, which measures the volume of gas collected [1].

(b) Completing the assembly gas-tight [2]. The join must be sealed at both ends:

1. Push a bung carrying the delivery tube firmly into the neck of the conical flask so no gas escapes at the top [1].
2. Connect the delivery tube to the nozzle of the gas syringe, clamp the syringe horizontally, and check the plunger is pushed fully in and reads zero before the solid is added [1].

Starting from zero with an airtight seal matters because any gas lost before or during collection makes the measured volume too low.

(c) What to record and how often [2]. Record two quantities: the volume of gas in the syringe and the time on the stop-clock [1]. Take the volume at regular intervals, for example every 30 s (any stated regular interval from 10 s to 60 s is acceptable), continuing until no more gas is collected [1]. Fixed intervals are needed so the readings can be plotted as a smooth volume-time graph from which the rate is read.

Exam takeaway: for any gas-collection rate experiment, name the two variables as volume and time, and always state a regular time interval rather than just saying you would time it.