The Characteristic Properties of Acids & Bases (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Chemistry): Flashcards
Exam code: 0654 & 0973
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Define "acid" in terms of the ions it produces in aqueous solution.
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Define "acid" in terms of the ions it produces in aqueous solution.
An acid is a substance that produces hydrogen ions, H+ (aq), when dissolved in water.
On the pH scale, acids have a pH ______ 7 and alkalis have a pH ______ 7.
On the pH scale, acids have a pH below 7 and alkalis have a pH above 7.
What three products form when an acid reacts with a metal carbonate?
When an acid reacts with a metal carbonate / salt, carbon dioxide and water are produced.
True or False?
All bases are alkalis.
False.
A base is any substance that neutralises an acid, but only bases that dissolve in water are called alkalis.
What is an alkali?
An alkali is a soluble base that produces hydroxide ions, OH- (aq), when dissolved in water.
When sodium hydroxide dissolves in water it dissociates to form Na+ (aq) and ______ (aq) ions, making the solution ______.
When sodium hydroxide dissolves in water it dissociates to form Na+ (aq) and OH^-^ (aq) ions, making the solution alkaline.
How does litmus indicator change colour in acidic and alkaline solutions?
In acidic solutions litmus turns red. In alkaline solutions litmus turns blue.
State the net ionic equation for all acid-base neutralisation reactions.
The net ionic equation is:
H+ (aq) + OH- (aq) → H2O (l).
True or False?
All reactions of acids are neutralisation reactions.
False.
When a metal reacts with an acid, a salt is produced but no water is formed, so it does not count as a neutralisation reaction.
The pH scale runs from 1 to 14. A pH of ______ is neutral, a pH below 7 is ______ and a pH above 7 is ______.
The pH scale runs from 1 to 14. A pH of 7 is neutral, a pH below 7 is acidic and a pH above 7 is alkaline.
Why does a solution become neutral when an acid and an alkali react in a neutralisation reaction?
The solution becomes neutral because H+ ions from the acid react with OH- ions from the alkali to form water, removing both types of ion from solution.
What does it mean for the pH scale to be logarithmic?
Each change of 1 on the pH scale represents a change in hydrogen ion concentration by a factor of 10.
Universal indicator is a mixture of ______ used to estimate ______ by matching colour to a chart.
Universal indicator is a mixture of indicators used to estimate pH by matching colour to a chart.
How does the concentration of H+ ions relate to pH?
As the concentration of H+ ions increases, the pH decreases — they have an inverse relationship.
Define "acidic oxide" and give two examples.
An acidic oxide is formed when a non-metal combines with oxygen. Examples include CO2 and SO2.
Metal oxides are ______ oxides; non-metal oxides are ______ oxides.
Metal oxides are basic oxides; non-metal oxides are acidic oxides.
True or False?
Basic oxides dissolve in water to produce a low pH solution.
False.
Basic oxides dissolve in water to produce an alkaline (basic) solution with a high pH, not a low one.
What is an amphoteric oxide?
An amphoteric oxide can react as both an acid and a base, depending on its reactant. In both cases a salt and water are formed.
Why is zinc oxide (ZnO) described as amphoteric?
Zinc oxide is amphoteric because it reacts with both acids and bases, forming a salt and water in each case.
Al2O3 reacts with HCl to form ______ and water, behaving as a ______ oxide.
Al2O3 reacts with HCl to form AlCl3 and water, behaving as a basic oxide.
What are neutral oxides and give two examples?
Neutral oxides do not react with acids or bases. Examples include N2O and CO.
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