Before starting a neutralisation experiment, a student measured the temperature of some dilute acid. Fig. 5.1 shows the thermometer used. (a) Record the tem...
Question 1 Report
Before starting a neutralisation experiment, a student measured the temperature of some dilute acid. Fig. 5.1 shows the thermometer used.
(a) Record the temperature shown on the thermometer in Fig. 5.1. [1]
(b) Name a piece of apparatus that could measure 25.0 cm3 of the acid accurately. [1]
(c) Name the type of container used to reduce heat loss during the experiment. [1]
(d) Suggest why the thermometer should be read at eye level. [1]
Answer Details
Reading a thermometer accurately is a basic practical skill: each small division must be counted, and the eye must be level with the top of the liquid to avoid a false reading.
(a) The liquid in Fig. 5.1 reaches the mark for 21.0 ℃ (accept 21 ℃) [1].
(b) To measure exactly 25.0 cm3 of acid accurately, use a volumetric pipette (a burette is also accepted) [1]; a measuring cylinder is not precise enough for a value quoted to one decimal place.
(c) Heat loss is reduced by using an insulated polystyrene cup [1], because polystyrene is a poor conductor of heat.
(d) The thermometer is read at eye level to avoid a parallax error, so the reading is accurate [1]. Looking from above or below makes the liquid line up with the wrong scale mark.
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