 |
You may well have carried out this experiment in class. When the calcium carbonate is added to the flask, it fizzes and bubbles. We are measuring the rate of reaction using change in mass, due to loss of gas.
Why might the bubbles cause our results to be wrong, and how would the cotton wool plug help in this regard? |
 |
In this question, the term average can be confusing. We call it an average rate because the rate is changing as the reaction proceeds in the first 10 seconds of the reaction, as shown by the changes in the values. ( A constant rate would produce a constant change).
The average rate is simply calculated in these circumstance by examining the change in quantity and dividing that by the time taken.
|
 |
At first sight this may appear daunting, but take time to reread the question, including the stem of the question carefully.
The information you require to answer this question is held in the stem of the question and the graph. You should appreciate that this is simply a more complicated presentation of a calculation based on equation, the type you were able to do at National 5 level. The balanced equation is provide in the stem of the question. From that you can establish a molar ratio between the copper (II) carbonate and carbon dioxide. The mass of carbon dioxide produced is obtained from the graph, and so the mass of copper (II) carbonate can be calculated. Don’t be put off by the complex way the question is presented. |
 |
