Limestone contains calcium carbonate (CaCO₃) - AQA - GCSE Chemistry - Question 5 - 2014 - Paper 1

To calculate the mean mass lost, we first need to find the individual mass losses:

• Experiment 1: 1.8 g
• Experiment 2: 1.0 g
• Experiment 3: 1.9 g
• Experiment 4: 1.7 g

Next, we add these values together:

$1.8 + 1.0 + 1.9 + 1.7 = 6.4 g$

Now, we divide by the number of experiments (4):

$\text{Mean mass lost} = \frac{6.4}{4} = 1.6 g$

However, considering anomalies (1.0 g from Experiment 2 is significantly lower), we will recalculate using the other values:

$1.8 + 1.9 + 1.7 = 5.4 g$

$\text{Adjusted mean} = \frac{5.4}{3} = 1.8 g$

1. Impurities in limestone: The limestone used may not have been pure calcium carbonate, resulting in less carbon dioxide being released than expected. Impurities could contribute to the overall mass, which would not decompose, thereby leading to a lower mass loss.

2. Insufficient heating: The limestone might not have been heated long enough or at a high enough temperature to fully decompose. If the reaction is incomplete, less carbon dioxide will be produced, resulting in a lower mass loss than the theoretical maximum.