Washing soda is added to hard water to allow soap to lather. A brand of washing soda contains partially hydrated sodium carbonate solid. A 0.300 g sample completely reacts with 20.0 mL of 0.250 M hydrochloric acid.

 

a) What mass of sodium carbonate was present?

 

b) Calculate the percentage by mass of sodium carbonate in the washing soda.

 

Please.

Any help would be appreciated!

How do I do this question? Would anyone be able to give me some hints/advice on how to tackle this question?

Edited March 30, 201114 yr by gerald_mcdonald

Washing soda is added to hard water to allow soap to lather. A brand of washing soda contains partially hydrated sodium carbonate solid. A 0.300 g sample completely reacts with 20.0 mL of 0.250 M hydrochloric acid.

 

a) What mass of sodium carbonate was present?

 

b) Calculate the percentage by mass of sodium carbonate in the washing soda.

 

Please.

Any help would be appreciated!

How do I do this question? Would anyone be able to give me some hints/advice on how to tackle this question?

 

a) is a moles question. Calculate the number of moles of HCl, then using a balanced equation work out the moles of Na₂CO₃. Once you've got the moles, you can work out the mass.

 

b) use your answer to part a to answer part be as a percentage.

Remember the trusty titration equation:

 

[math] M_{1}V_{1} = M_{2}V_{2} [/math]

 

Where V is volume and M is moles. Also remember the sodium carbonate is a diprotic base so adjust the above expression accordingly to account for stoichiometry.