Q16.
TWO correct extrapolations of best fit straight lines
Max 5/7 if no extrapolations or best fit straight lines
drawn
1
Use of their lines to calculate the temperature change at the 4th minute
1
(17 °C)
Q = mcΔT
Q = 10 × 4.18 × [student’s temperature change]
Q = [710.6 J]
Correct numbers inserted into expression.
1
Moles of Mg = 0.24 / 24.3 = 0.00988 mol
1
ΔH = 710.6 / 0.00988 = 71923.07 J mol−1
1
ΔH = –72 (kJ mol−1)
Must be negative to score M6
1
Answer to 2 significant figures
1
[7]