We have discussed on the similarities & differences between Insoluble Bases & Soluble Bases (aka Alkalis) for O Level Chemistry.
Alkalis have more uses in our everyday lives as well as industrial application. As such, we will look into its Physical & Chemical Properties.
PHYSICAL PROPERTIES OF ALKALIS:
1. Alkalis have a BITTER taste & have a SOAPY touch
2. Alkalis turn RED litmus paper BLUE
3. Alkalis have a pH value > 7
4. Alkalis are CAUSTIC
5. Alkalis CONDUCT ELECTRICITY due to the presence of MOBILE IONS in solution
CHEMICAL PROPERTIES OF ALKALIS:
1. Neutralization Reaction (Dilute Acid + Alkali –> Salt + Water)
2. Alkali react with Ammonium Salts to produce Ammonia Gas when heated gently
Alkali + Ammonium Salt –> Salt + Ammonia Gas + Water [Heat gently]
3. Precipitation of Insoluble Metal Hydroxides from aqueous solutions containing salts using common alkalis such as NaOH & NH4OH
Metal Ions in Solution + Alkali –> Insoluble Metal Hydroxide (PRECIPITATES)
We will discuss more of this under future posts on QUALITATIVE ANALYSIS.
Let’s try out some exam-based questions to see how much you have learnt today.
Quick Check 1:
In which of the following pairs would the two substances react to form a salt and water only?
A. iron and steam
B. aqueous sodium carbonate and dilute sulphuric acid
C. aqueous sodium chloride and aqueous silver nitrate
D. aqueous sodium hydroxide and dilute ethanoic acid
E. zinc and dilute hydrochloric acid
Quick Check 2:
Name the products obtained when calcium oxide is:
(b) dissolved in dilute HCl
(c) heated in ammonium chloride
PS: Do leave your suggested answers in the “Comments Section” directly below this post.
PPS: This post belongs to a series of blogposts that is associated with Secrets of “Acids, Bases & Salts and Qualitative Analysis revelaed”
Not sure correct but for
1. D because its an acid-base reaction giving salt + water only
2b. Calcium chloride and water
2c. Calcium chloride + ammonia gas + water
Reply
sean Reply:
September 8th, 2008 at 12:42 pm
Hi Sherman,
Well Done. Keep up the good work!
All The Best To Your Academic Success in Chemistry
Sean
Master Trainer
Reply
For the first question, the answer is D, because it is an acid-base reaction and the products are a salt and water.
In 2b: the products are Calcium Chloride and Water and,
in 2c: the products are Calcium Chloride, Water and Ammonia Gas.
Reply
sean Reply:
May 6th, 2010 at 12:36 am
Well Done! Keep it up and continue learning!
Reply
sean i don’t understand this reaction.can u please explain!!
3. Precipitation of Insoluble Metal Hydroxides from aqueous solutions containing salts using common alkalis such as NaOH & NH4OH
Metal Ions in Solution + Alkali –> Insoluble Metal Hydroxide (PRECIPITATES)
Reply
sean Reply:
May 6th, 2010 at 12:35 am
This is covered under Qualitative Analysis (QA) specifically on the Testing for Cations.
Reply
D is the answer?
Reply