Emergency help!! How do I answer these correctly? I\'m doing a titration with so

Question

Emergency help!! How do I answer these correctly? I'm doing a titration with sodium carbonate and hydrochloric acid. Excess acid is then titrated with NaOH.

1) Total moles of HCl = moles of HCl reacted with Na2CO3 + moles of HCl. How will you determine the total of moles of HCl added to the flask?

2) How will you determine the moles of titrant at the end point of the titration?

3) At the equivalence point, do moles od titrant equal the moles of total HCl, excess HCl, or HCl reacted with sodium carbonate? How do you know?

4) How will you determine the percent mass of sodium carbonate in soda ash?

5) The titration is performed on the excess (remaining) HCl. What reaction occurs during the titration?

thank you so much in advance for answering. I really appreciated and will vote/comment on your answer.

Explanation / Answer

1]

Total moles of HCl = moles of HCl reacted with Na2CO3 + Moles of NaOH

Because excess acid is titrated with NaOH

HCl + NaOH ----> NaCl + H2O

Here ;

Moles of HCl = Moles of NaOH

2]

At the end point ;

2HCl + Na2CO3 -----> 2NaCl + H2O + CO2

Equivalents of HCl and Na2CO3 are equal or

For example ;

If 3 moles of HCl are required for neutralisation then moles of Na2CO3 present in the sample is 3/2

3]

Equivalence point :  The equivalence point is the point in a titration where the amount of titrant added is enough to completely neutralize the analyte solution.

Answer is Moles of HCl reacted with Na2CO3

4]

Mass percent = Moles of Na2CO3 [or Moles of HCl/2] *MW of Na2CO3 *100 / Mass of sample

5]

HCl + NaOH -----> NaCl + H2O

Acid - Base reaction [Neutralisation reaction ]

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