The leaf compost jar and the control jar both contained the same initial volume

Question

The leaf compost jar and the control jar both contained the same initial volume and concentration of NaOH. Explain why the control jar required a larger volume of HCl than the leaf compost jar did to reach the end point of the titration. A pair of students forgets to precipitate the carbonate ions in their leaf compost jar's NaOH solution prior to the HCl titration. How would this affect the perceived amount of NaOH present in the titrand? The perceived amount of NaOH would be higher than wht it actually is. The perceived amount of NaOH would be lower than what it actually is. Explain your answer. How would forgetting to precipitate the carbonate ions affect the perceived amount of CO_2 off by the leaves? The amount of CO_2 would be perceived higher than what it actually is. The amount of CO_2 would be perceived lower than what it actually is.

Explanation / Answer

1) Leaf compost (carbon –containing bio-matter) releases CO2 by its aerobic and anaerobic decomposition.The CO2 released, in contact with water form carbonic acid ,which neutralizes some amount of base (NaOH) added, (apart from NaOH being used up in HCl neutralization). So more amount of NaOH is required in leaf compost jar.

CO2 +H2O=H2CO3 (carbonic acid)

2)a)The perceived amount of NaOH would be higher than what it actually is. (for reason same as part a)

3)a) The amount of CO2 would be perceived higher than what it actually is.( Reason -no carbon dioxide is converted to carbonated rather sodium carbonate salt by reaction with NaOH)

2NaOH +CO2   =Na2CO3 +H2O

2NaOH +H2CO3 =Na2CO3 +2H2O

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