2 test tubes ● 2 mol dm–3 dilute hydrochloric acid ● solid potassium carbonate ● solid potassium hydrogencarbonate ● thermometer able to read up to 50 °C or more ● polystyrene cup ● 250 cm3 or 400 cm3 beaker ● burette, clamp and stand ● stirring rod ● mass balance (2 d.p.) ● spatula
Place approximately 3 g of solid potassium carbonate into a test tube. Accurately weigh the test tube and its contents.
2. Use a burette to dispense 30 cm3 of 2 mol dm–3 hydrochloric acid into a polystyrene cup, which is supported in a beaker.
3. Measure the temperature of the acid.
4. Continue measuring the temperature whilst adding potassium carbonate to the acid and stirring. Record the highest temperature reached.
5. Reweigh the empty test tube.
6. Repeat steps 1 to 5 using approximately 3.5 g of potassium hydrogencarbonate instead of potassium carbonate. This time record the lowest temperature reached.
Correctly use appropriate instrumentation, apparatus & materials to carry out experimental technique with minimal assistance or prompting
· Follows given method using appropriate equipment with minimal assistance
CPAC 4a – Makes accurate observations relevant to the experimental procedure
· Read from bottom of meniscus when using burette (teacher to check)
· Read masses to at least 2dp’s (teacher to check)
· Read thermometers correctly
· Read scales correctly on all pieces of apparatus
Wear goggles.
2 mol dm–3 hydrochloric acid is an irritant.
Potassium carbonate is an irritant.
CPAC 3b – Uses appropriate safety equipment and approaches to minimise risks with minimal prompting
· Collect all eqpt at start to minimise walking around the lab once practical work
· Set up work space in an organised fashion and safe
· Fill burette using funnel below eye level & without overflowing
· Wear safety goggles & lab coats throughout
· No spillages/deals with spillages appropriately with minimal fuss
· Keep stoppers on bottles when not in use
· Hold test tubes in racks (to prevent rolling off the table & smashing)
· Stand cup in appropriate sized beaker to stabilize (which may be clamped to increase stability)
· Measure out powders next to balance to prevent walking round lab with bottles/open containers of powders
· Discuss medical issues prior to practical work that may need considering (ie asthmatic/ epileptic…)
· Correctly dispose of reaction mixture (reagents & products) at end of practical
· Keep area tidy & clear away properly & cleaned down (if needed) for following students without prompting
Consult CLEAPSS Hazcards® 47A, 95A. Perform a risk assessment using up-to-date information before this practical is carried out