HSC 2010 Q 26 Method to Get Chemical Formula

[frog1944]

Hi,

I was attempting to do question 26 from the 2010 HSC Chemistry exam, whilst I got the "correct" answer, using acid + metal -> salt + hydrogen gas. The actual correct answer (not necessarily what the HSC examiners marked on), was that the chemical equation was actually meant to be 3Zn + 8HNO3 -> 3Zn(NO3)2 + 2NO + 4H2O, this "uses the correct chemical change" (as per the excel past papers book). I was curious how we would figure the following out in the HSC? If a similar question came up again this year in the HSC (not necessarily zinc), would you just go acid + metal -> salt + hydrogen gas, or would you do whatever way they got the above?

Thanks

[tigerkher]

That seems outside the scope of the syllabus, and even I didn't learn that when I did the HSC. Your method is what I'd expect to be used to answer this question. So, the reaction would be:

Zn (s) + 2HNO3 (aq) --> Zn(NO3)2 (aq) + H2 (g)

Also, if you haven't gotten the habit of doing so already, remember to add the states of reactants and products, to every single chemical equation you write.

[frog1944]

Thanks, will do!