Summary AQA A Level Chemistry - All Chemical Tests with Reagents and Observations
28 views 1 purchase
Course
All units (7405)
Institution
AQA
A level chemistry exams will often require you to describe a chemical test, in which you will need to be able to identify the reagent required, the observations and the species produced. This document provides a summary of these reactions, along with the aforementioned details. Having these details...
Testing for Cations
Testing for Group 2 Ions
Using Hydroxide Ions:
• Reagent: NaOH
• Observations:
Group 2 Ion Initial Solution 10 Drops of NaOH Excess NaOH
2+
Magnesium, Mg Colourless Slight White Precipitate White Precipitate
Calcium, Ca2+ Colourless Slight White Precipitate Slight White Precipitate
Strontium, Sr2+ Colourless Slight White Precipitate Slight White Precipitate
Barium, Ba2+ Colourless No Change No Change
• Group 2 hydroxides become more soluble down the group.
• Mg(OH)2 is insoluble in water, so forms a white precipitate.
• Ca(OH)2 is partially soluble in water, so forms a slight white precipitate.
Using Sulfate Ions:
• Reagent: H2SO4
• Observations:
Group 2 Ion Initial Solution 10 Drops of H2SO4 Excess H2SO4
Magnesium, Mg2+ Colourless Slight White Precipitate Colourless
Calcium, Ca2+ Colourless Slight White Precipitate Slight White Precipitate
Strontium, Sr2+ Colourless White Precipitate White Precipitate
Barium, Ba2+ Colourless White Precipitate White Precipitate
• Group 2 sulfates become less soluble down the group.
• BaSO4 and SrSO4 will form white precipitates due to their low solubilities..
Testing for Group 3 Ions
• Reagent: NaOH
• Observation: white precipitate of aluminium hydroxide:
o [Al(H2O)6]3+ (aq) + 3OH– (aq) ! Al(H2O)3(OH)3 (s) + 3H2O (l)
• Reagent: Excess NaOH
• Observation: The precipitate will dissolve in excess sodium hydroxide to form a colourless solution:
o Al(H2O)3(OH)3 (s) + OH– (aq) ! [Al(OH)4] – (aq) + 3H2O (l)
Test for Ammonium Ions
• Reagent: NaOH
o Adding hydroxide ions to a solution with ammonium ions will form ammonia gas:
• Observation: Ammonia gas is alkaline, so will turn damp red litmus paper blue.
o NH4+ + OH–! NH3 + H2O.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller JunaidAli025. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $5.15. You're not tied to anything after your purchase.
