iGCSE Chemistry (0620) Core:12.1 Experimental design: Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
The graph shows the volume of hydrogen gas produced over time during a chemical reaction. To measure the volume of gas produced, a gas syringe is the most appropriate apparatus—it allows accurate measurement of gas volume as the reaction proceeds. The stop-watch is used to measure time intervals. A beaker cannot accurately measure gas volume, a pipette is used for measuring and transferring specific volumes of liquids, and a test-tube is used for holding small amounts of substances but cannot measure gas volume. Therefore, the other item of apparatus needed alongside the stop-watch is a gas syringe, making option B correct.
▶️ Answer/Explanation
Detailed solution:
To measure the effect of temperature on reaction rate, you absolutely must measure temperature (to see what temperature you’re testing) and time (to see how fast the reaction happens). So, a stop-watch and a thermometer are essential. A balance is for mass, and a gas syringe is for collecting a gas—neither is needed for *any* reaction, as you could be measuring colour change or mass loss instead. For this specific aim, time and temperature are the only must-haves.
▶️ Answer/Explanation
Detailed solution:
To measure a volume as precise as $25.00\,\mathrm{cm}^3$ (i.e., to two decimal places), a high-precision apparatus is needed. A burette is graduated in $0.1\,\mathrm{cm}^3$ intervals, allowing the user to read volumes to the nearest $0.05\,\mathrm{cm}^3$, making it suitable for such accurate measurements. A beaker gives only approximate volumes, a measuring cylinder is less precise (typically to the nearest $0.5\,\mathrm{cm}^3$), and a dropping pipette is not calibrated for specific volumes.