# Finding the percentage of composition in the mixture

Homework Statement:
A mixture of calcium carbonate and magnesium carbonate weighs 2.36 g. It is dissolved in a 700 ml, 0.10 moles per cubic decimeter Hydrochloric solution. The resulting solution is then diluted up to 25 cubic decimeter with water. 20 ml of sodium hydroxide completely reacts with 25 ml of above prepared solution. Find the percentage composition of composition of the mixture.
Relevant Equations:
C = n/v , C1V1=C2V2 , number of moles = mass/molar mass ..... I don't know what other equations appear here.
The thing is that, I don't know how to approach this question and the particular steps for relevant value findings. Please show me the path, and I will go in it friends. I couldn't attempt as I have no clue how to approach this. Thank you very much in advance.

Ygggdrasil
Gold Member
The titration with sodium hydroxide will tell you how much HCl remains in solution after reaction with the carbonate mixture. Therefore, a good starting point is to calculate how much HCl reacted with NaOH in the last step in order to infer how much HCl reacted with the carbonate mixture.

nineteen
The titration with sodium hydroxide will tell you how much HCl remains in solution after reaction with the carbonate mixture. Therefore, a good starting point is to calculate how much HCl reacted with NaOH in the last step in order to infer how much HCl reacted with the carbonate mixture.

Yeah I did that, thank you very much. Hey are the number of moles of MgCO3 and number of moles of CaCO3 equal ? I could come to a solution but I don't know whether it is correct or not. Are the number of moles of the both equal?

What should I do after finding the excess amount of HCL present in the mixture that was diluted up to 25 dm3?

symbolipoint
Homework Helper
Gold Member
Targeting only for carbonate will not be enough information if you are looking for both how much Mg and how much Ca.

Borek
Mentor
Assume x moles of magnesium carbonate and y moles of calcium carbonate.

Titration told you x+y.

Can you express sample mass with x, y?