Answer :
I can help with writing the balanced equation and answering some of your questions related to the reaction of hydrochloric acid with calcium carbonate.
The balanced chemical equation for the reaction between hydrochloric acid (HCl) and calcium carbonate (CaCO3) is:
\[ 2HCl + CaCO3 \rightarrow CaCl2 + H2O + CO2 \]
Now, let's address your questions:
3.3) To find the mass of carbon dioxide gas formed after 8 minutes, we need additional information such as the rate of the reaction. Without this information, it's not possible to determine the exact mass of CO2 formed.
3.4) The reaction rate is the highest during the time interval when the slope of the graph is steepest. In an exothermic reaction like this one, the rate of reaction is typically highest at the beginning (0-2 minutes) when the reactants are in their highest concentration and the temperature is also usually highest at the start of the reaction.
3.5) To determine the time at which half of the CaCO3 has reacted, you would need to observe the graph and find the point where the amount of CaCO3 has decreased by half. This point corresponds to the time at which half of the CaCO3 has reacted.
6) Predicting the rate of reaction changes:
 - 3.6.1) If marble pieces are replaced by marble powder, the rate of reaction would likely increase. This is because marble powder has a larger surface area compared to marble pieces, providing more surface for the reaction to occur.
 - 3.6.2) Using a 2 mol/dm³ hydrochloric acid solution instead of a 1.5 mol/dm³ solution would also likely increase the rate of reaction. Higher concentration of reactants generally leads to faster reaction rates, as there are more reactant particles available to collide and react.
If you have specific data or more details about the experiment, I can provide more accurate answers and calculations.
