[ronnie]

Would you please answer the following Q ?

0.949 g of mixture NaOH & NaCO3 dissolve in 100 cm3 Water. Then 30cm3, 0.65M HCL added into it for complete neutralization.
Calculate the percentage of NaOH, NaCO3 respectively ?

Please show the steps ~

thanks ~

[Borek]

You have to set up a system of two equations - one will be mass + mass, second will be number of moles + number of moles. You have two unknowns - be it masses of both substances - that can be inserted into these two equations (hint: you will need their molar masses).

You also better read forum rules:

http://www.chemicalforums.com/index.php?topic=59.0

[Qazzian]

Should that be NaHCO3, or Na2CO3?

[Borek]

Should that be NaHCO3, or Na2CO3?

Does it matter?

[Qazzian]

Wouldn't it matter for the number of moles HCl to neutrilize it?

[Albert]

There's nothing wrong in the opening post. Except for the lack of attempts.

[xiankai]

even if the Na2CO3 became NaHCO3, amt of HCl used will be the same;

Na2CO3 = 2NaHCO3 = 2HCl

unless the water happens to acidify the sodium carbonate... maybe?

[Borek]

Wouldn't it matter for the number of moles HCl to neutrilize it?

What I mean is - it matters for the final result, but it doesn't change methodology needed to solve the question.

[Borek]

even if the Na2CO3 became NaHCO3, amt of HCl used will be the same;

Na2CO3 = 2NaHCO3 = 2HCl

Think it over - x moles of carbonate requires twice more HCl than x moles of hydrogen carbonate.

[xiankai]

oh wait u mean something like this happens?

Na₂CO₃ + H₂O --> NaHCO₃ + NaOH

in that case i made a mistake... i was thinking more along the lines of

Na₂CO₃ + 2H+ --> 2NaHCO₃

:S

[Borek]

No, you have two reactions taking place (in fact there are three - carbonates react in two steps - but it doesn't matter for the final result):

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

[xiankai]

oh i understand now... intially i was thinking that the only way that NaHCO₃ could be formed was via the decomposition of Na₂CO₃, but after re-reading the entire thread i realise its all due to a typo error in the first place, thanks Borek!

<resolves to read posts more caerfully in the future>




Edit: missing 2 added