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HSC Chemistry Question Thread

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milie10:

--- Quote from: r1ckworthy on January 30, 2020, 06:59:02 pm ---Hey!You are right! 10L is the answer, so you choose the answer that is closest to this value, which is C!
Here is my working out of the question (click on the image to make it larger):
(Image removed from quote.)
When you use \( n=c \times v \), it only finds n(HCl). I find limiting reagent questions confusing, so I like to write statements as I did in my working. In those statements, I calculated how many moles a substance will react with/ use up (according to stoichiometric ratios). I compare the two statements and pretty quickly find out which substance is the limiting reagent.
I am not sure of a quicker way to do this question (hopefully someone can chip in!).

Let me know if you need any more help!

--- End quote ---

Thanks heaps, that clears things up!! Writing the limiting reagent statements really helps- I'll start doing that. :D
* Noticed a trivial mistake in your working- HCl leftover = 0.002- 0.0008 =0.0012

r1ckworthy:

--- Quote from: milie10 on January 30, 2020, 10:37:40 pm ---Thanks heaps, that clears things up!! Writing the limiting reagent statements really helps- I'll start doing that. :D
* Noticed a trivial mistake in your working- HCl leftover = 0.002- 0.0008 =0.0012

--- End quote ---

Oops! Not surprised though, did rush a lot ;D Glad it was of help to you!

milie10:
Hi!

I'm a bit confused about why CaCO3 is a basic salt instead of neutral. Could someone explain this please?

Thanks! :)

r1ckworthy:

--- Quote from: milie10 on February 02, 2020, 12:58:59 am ---Hi!

I'm a bit confused about why CaCO3 is a basic salt instead of neutral. Could someone explain this please?

Thanks! :)

--- End quote ---
Hey!

It all has to do with how \( \text{CaCO}_3 \) dissociates in water. \( \text{CaCO}_3 \) dissociates in water to produce \( \text{Ca}^\text{2+} \) and \( \text{CO}_3^\text{2-} \) ions. The  \( \text{CO}_3^\text{2-} \) ions react with water to produce \( \text{HCO}_3^- \) and hydroxide ions, which leads the solution to be basic.

BlackFrost:
In an experiment of separating sand from salt water (which involves filtration and evaporation), what could be the sources of errors that could eventually cause substances to be lost ?

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