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secondary 3 | E Maths
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Wesley
Wesley

secondary 3 chevron_right E Maths chevron_right Singapore

help with this eqn pls

Date Posted: 1 month ago
Views: 13
Eric Nicholas K
Eric Nicholas K
1 month ago
Should be NH4Cl only.

NH3 is a basic gas, HCl is an acid, and the direct compound formed is NH4Cl.

It would not be appropriate to include water as the product in the equation as this leads to an imbalance of atoms on both sides (since oxygen “magically” appears out of nowhere).

But dissolve NH3 in water to get the alkaline NH4OH and your product will also contain water (think of the ions present in these compounds).
Wesley
Wesley
1 month ago
thanks sooo much
J
J
1 month ago
https://www.quora.com/What-is-the-reaction-between-NH3-and-HCl

This is actually a fairly common reaction of 2 gases. Both NH3 and HCl are gases here.

So HCl is not in acid form i.e not dissolved in water/no water present.

So the only product is NH4Cl
Eric Nicholas K
Eric Nicholas K
1 month ago
The given blanks _____ + _____ seem misleading though
J
J
1 month ago
It's meant to test the students in their concepts. I.e if there's only 1 product, leave 1 blank empty. Two blanks doesn't always mean two products
J
J
1 month ago
Edit :

Maybe the teacher is talking about aqueous ammonia and hydrochloric acid. But that would result in 1 product as well.

The problem is no state symbols are given in the question.
Eric Nicholas K
Eric Nicholas K
1 month ago
But it’s weird if they put the express NH3 as aq, so NH3 has to be a gas.

Aqueous ammonia is basically ammonium hydroxide.
J
J
1 month ago
Ah I noticed a star beside the question. So I reckon it's meant to be a tougher question
J
J
1 month ago
Not really. Aqueous ammonia is actually a solution of ammonium ions and hydroxide ions.

I.e doesn't exist as a NH4OH formula unit. In the past for my time we were instructed not to write NH4OH.

I would offer two equations for this question :

NH3(g) + HCl (g) → NH4Cl (s)

NH3(aq) + HCl (aq) → NH4Cl (aq)
Eric Nicholas K
Eric Nicholas K
1 month ago
But technically the reaction NH3 + H2O to become NH4OH comes with some equilibrium since the reaction is reversible, so it does exist in both forms (and their ions) at any point of time.

I could not remember whether my syllabus required me to write NH4OH or avoid writing it.
J
J
1 month ago
NH3 doesn't have to be in gaseous form only. It is quite common to see NH3(aq)
J
J
1 month ago
Strictly speaking NH4OH doesn't exist .

The correct equilibrium equation is

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH- (aq)

The two ions are detached and not bound to each other as suggested in NH4OH
Eric Nicholas K
Eric Nicholas K
1 month ago
True
J
J
1 month ago
I should add that ammonia gas first is dissolved in water to form aqueous ammonia.

I.e

NH3(g) → NH3(aq)

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