practical questions (2)

Question 1

describe a procedure to calculate enthalpy changes (calorimetry) [6 marks]

Answer 1

• measure a fixed volume of water, place it in a calorimeter + measure its initial temp. using a thermometer
• measure the initial mass of the alcohol in the spirit burner; light the spirit burner + heat the water
• when the temp. of the water rises by about 20C, put out the flame + measure the final temp. of the water
• measure final mass of alcohol in the spirit burner
• use Q=mcT to find energy transferred

Question 2

how to calibrate a pH curve?

Answer 2

• rinse pH probe with distilled water
• dip pH probe into a buffer solution + wash probe in distilled water
• dip probe in buffer solution with a DIFFERENT pH
• calibrate a pH probe + use to measure the initial pH of the alkali in the concial flask