Help with Stoichiometry and Volumetric Analysis

[kara]

I need some help with this question.

A piece of chalk (mainly calcium carbonate) is placed in 250 mL of 0.293 M HCl. All the CaCO3 reacts, realising CO2 gas, and leaving a clear solution. 50.00 mL of the solution is pipetted into another flask. 87.1 mL of 0.0567 M NaOH is required to titrate the HCl remaining in this 50.00 mL portion. What was the original mass of CaCo3 in the piece of chalk?

So far I've found balanced chemical equations from the question... they are:

1. CaCO3 + 2HCl --> CaCl2 + CO2 + H2O

2. HCl + NaOH --> NaCl + H2O

Where should i go from there, the info given is really overwhelming.

 

[GCT]

You should be able to determine the moles of HCl that had reacted with the CaCO3, to do this you need to know the original, total, moles of HCl and the amount that remained after the reaction with CaCO3.

 

[Blueshift5]

Stoichiometry and Volumetric Analysis can be complex topics, so it's understandable that you may need some help with this question. Let's break down the information given and go step by step to solve the problem.

First, we have a piece of chalk (mainly calcium carbonate) and we know that it reacts with 0.293 M HCl according to the balanced chemical equation: CaCO3 + 2HCl --> CaCl2 + CO2 + H2O. This means that for every 1 mole of CaCO3, 2 moles of HCl are required for the reaction to occur.

Next, we are told that all of the CaCO3 reacts, releasing CO2 gas and leaving a clear solution. This means that we have a complete reaction and there are no excess reactants or products.

Then, 50.00 mL of the solution is pipetted into another flask and we are given the volume and concentration of NaOH required to titrate the HCl remaining in this 50.00 mL portion. This means that the NaOH is reacting with the excess HCl in the solution.

Using the second balanced chemical equation provided, HCl + NaOH --> NaCl + H2O, we can determine the moles of HCl present in the 50.00 mL portion of the solution. From there, we can use stoichiometry to calculate the moles of CaCO3 that reacted in the original solution.

Once we have the moles of CaCO3, we can use its molar mass to calculate the original mass of CaCO3 in the piece of chalk.

I hope this helps guide you in the right direction. Remember to always carefully analyze the given information and use balanced chemical equations to set up your calculations. If you're still struggling, don't hesitate to seek out additional resources or assistance from a teacher or tutor. Good luck!