Question Constellation Sign up for free

AQA · GCSE · Chemistry · Higher

Instantaneous reaction rate from a graph

Q05.7 4 marks

Figure 6 shows the results for sulfur trioxide.

Figure 6
Figure 6

Figure 6

Enlarged question image

Figure 6

Determine the rate of reaction at 60 seconds.

Practice unavailable

This question can be viewed, but its original response format is not available for practice yet.

Write your answer first. You can study the marking guidance whenever you need it.

Study the marking See what earns credit and compare it with a full-mark answer.

Marking points

  1. 1 Draws a tangent to the curve at 60 s.
  2. 2 Reads a valid y-step and x-step from that tangent within the official coordinate tolerance.
  3. 3 Divides the change in moles by the change in time.
  4. 4 Calculates the rate correctly in mol/s from the learner’s tangent readings.

Why this answer loses marks

Divide two readings taken directly from the curve.

That gives an interval average; at one instant, draw a tangent and use two points on that tangent.