C8 Acids, bases and salts - 1 & 2 Flashcards
What is an acid?
An acid is a substance that dissolves in water to produce hydrogen. - positively charged hydrogen ions H^+.
pH below 7.
What are examples of acids?
Hydrochloric acid (stomach) and citric acid.
What is a base?
A base is a substance that dissolves in water to produce hydroxide (ions).
OH^-
What are alkalis?
Alkalis are bases that are dissolved in water.
What are examples of bases?
Calcium carbonate (limestone) and sodium chloride (salt).
What does the pH scale show?
The pH scale shows how acidic an object is.
0-6 is acidic.
7 is neutral.
8-14 are bases.
What test can we use to investigate whether a substance is acidic or basic?
We can use the litmus paper test.
What is litmus paper?
Litmus paper is a thin strip of paper which comes in colours of blue and red.
Explain the litmus paper test.
Dip the litmus paper in the solution you want to test it. RED = ACIDIC.
BLUE = BASIC.
Litmus paper comes in both red and blue so there is still a result even if it stays those colours.
What is another acid-alkali indicator?
Another acid-alkali indicator is the universal indicator. The universal indicator turns different colours based on substances’ pH values.
What colours does the universal indicator turn?
It will turn red-yellow shades when tested with ACIDS.
It will turn purple-blue shades when tested with ALKALIS.
What can acids do?
Acids can neutralise a base, forming a salt and water.
Do all metals react with acids?
No, not all metals will react with acids. Only metals that are more reactive than hydrogen.
What two products are formed in a reaction with acids and metals?
Salt and hydrogen.
What reaction occurs with acids and metals? -MASH
MASH:
Metal + acid => salt + hydrogen
What may we observe during a reaction between a metal and acid?
You may observe fizzing which is the hydrogen gas. - introduce lit splint to reaction. If a “squeaky pop” occurs, it is hydrogen.
How to test for hydrogen gas?
The test for hydrogen gas is using a lit splint and if the gas burns with a “squeaky pop”, hydrogen is present.
What happens when a metal (magnesium) react with hydrochloric acid?
magnesium + hydrochloric acid => magnesium chloride + hydrogen
What salts does sulfuric acid produce?
Sulfuric acid produces sulphate salts.
What salts does nitric acid produce?
Nitric acid produces nitrate salts.
What salts does hydrochloric acid produce?
Hydrochloric acid produces chloride salts.
What type of bases can acids react with?
Acids will react with bases:
-Metal oxides
-Metal hydroxides
In the neutralisation reaction (acid and base), what two products are formed?
Water and salt.
What needs to be produced for it to be a neutralisation reaction?
Water.
What reaction occurs between a base and acid? BAWS
BAWS:
Base + acid => water + salt
What happens when a metal oxide (calcium) reacts with sulfuric acid?
Calcium oxide + sulfuric acid => water + calcium sulfate
What products are formed when an acid reacts with carbonates?
3 products are formed in a neutralisation reaction:
Water, carbon dioxide and salt.
What reaction occurs between a carbonate reacts and an acid? CAWCS
CAWCS
Carbonate + acid => water + carbon dioxide + salt
What reaction occurs when a carbonate (zinc) react with nitric acid?
Zinc carbonate + nitric acid => water + Carbon dioxide + zinc nitrate.
The carbon dioxide will turn limewater cloudy.
What is a carbonate?
A carbonate is a salt of carbonic acid.
What is the test for carbon dioxide?
Carbon dioxide will turn limewater cloudy.
How to test for the presence of a carbonate?
You can test for the presence of a carbonate by reacting it with an acid as the solution will turn cloudy from the carbon dioxide produced in the reaction.
What do the two colour indicators contain?
The two colour indicators contain organic compounds that appear different colours in acids and alkalis.
What are the two colour indicators?
-Litmus
-Thymolpthalein
-Methyl orange
What colours is thymolpthalein in acids and alkalis?
In an acid, it’s colourless.
In an alkali, it’s blue.
what colours is methyl orange in acids and alkalis?
In an acid, it’s red.
In an alkali, it’s yellow.
What happens when ammonium salts (containing NH4+ ions) is warmed with an alkali (bases)?
When ammonium salts are warmed with an alkali, they undergo decomposition.
What is formed when an alkali (base) react with ammonium salts?
A salt is formed.
What reaction can be used to test for the presence of ammonium ions?
NH4Cl + NaOH => NaCl + H2O + NH3
Ammonium salt reacts with a base and results in the formation of a salt and ammonia gas with water as a by product.
The ammonia gas will turn damn litmus paper from red to BLUE if ammonium ions are present.
Why is it important to control acidity in the soil?
The soil is necessary to grow crops, so it needs to be neutral. If it is too alkaline or acidic, the crops won’t grow properly.
What can be used to neutralise the soil?
Acidity is usually the problem for soil so spraying a base on it can help neutralise it. Bases like limestone and slaked lime are usually sprayed in the soil to neutralise it before planting crops.
What is formed when acids are added to water?
When acid are added to water, they from positively charged hydrogen ions - H^+
What does the presence of H^+ ions make a solution?
The presence of H^+ ions makes a solution acidic.
What is formed when alkalis are added to water?
When alkalis are added to water, they form negative hydroxide ions - OH^-
What does the presence of OH^- ions make an aqueous solution?
The presence of the OH^- ions is what makes the aqueous solution an alkali.
Define acids in terms of proton transfer.
Acids are proton donors as they ionise in solution producing protons, which are H^+ ions.
These H^+ ions make the aqueous solution acidic.
Define bases in terms of proton transfer.
Bases are proton acceptors as they accept the protons which are donated by the acid.
What are oxides?
Oxides are compounds made from one or more atoms of oxygen combined with one other element.
What are done with H^+ ions?
H^+ ions are donated to bases from acids.
What are examples of oxides?
MgO, ZnO, H2O.
How can oxides be classified?
Oxides can be classified based on their acid-base characteristics.
Why do acidic and basic oxides have different values of pH?
The difference in their pH stems from whether they are bonded to a metal or non-metal element.
Where are the metals on the periodic table?
The metals are on the left of the periodic table.
Where are the non-metals on the periodic table?
The non-metals are on the right of the periodic table.
What are acidic oxides formed with?
Acidic oxides are formed when a NON-metal element combines with oxygen.
They react with bases to form a salt and water.
-BAWS
What are basic oxides formed with?
Basic oxides are formed when a METAL element combines with oxygen.
They react with acids to form a salt and water.
-BAWS.
What are neutral oxides?
neutral oxides are those that do not react with either acids or bases and are thus said to be neutral.
E.g. CO.
What are amphoteric oxides?
Amphoteric oxides are a curious group of oxides that can behave as both acidic and basic, depending on whether the other reactant is an acid or a base.
What is formed with amphoteric oxides in both cases?
In both cases, salt and water are formed with amphoteric oxides.
