Question 17N.3.sl.TZ0.1
| Date | November 2017 | Marks available | [Maximum mark: 4] | Reference code | 17N.3.sl.TZ0.1 |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Outline, Sketch, State, Suggest | Question number | 1 | Adapted from | N/A |
A student set up a simple voltaic cell consisting of a copper electrode and a zinc electrode dipped in sodium chloride solution.
The student gradually increased the distance, d, between the electrodes to study the effect on the initial current, I, passing through the light bulb.
The student hypothesized that the initial current would be inversely proportional to the distance between the electrodes.
Sketch a graph that would support the student’s hypothesis.
[1]
OR
OR
Correct labels of axes required for mark.
Accept d–1 instead of .
Accept I–1 instead of .
Plot of I vs d should not be linear.
The following data was collected over five trials.
The data did not support the student’s hypothesis. He investigated other possible relationships by plotting a graph of the average current against the distance between the electrodes. He obtained the following best-fit line with a correlation coefficient (r) of −0.9999.
Suggest what the correlation coefficient of −0.9999 indicates.
[1]
negative correlation
OR
model/prediction matches results
OR
99% of variance accounted for
State the equation of the straight line obtained using the data.
[1]
I = – 0.001631 d + 0.09939
OR
y = – 0.001631 x + 0.09939
Accept correctly rounded values for m and b in equation.
Do not accept “y = mx + b”.
Outline how current flows in the sodium chloride solution.
[1]
ions move «across electrolyte»