Acids Bases and Salts Flashcards
What is the name of the scale which decides which substances are acids and alkali?
pH
What number is neutral on the pH scale
7
What side of the pH scale are alkalis?
Under 7
What do acid solutions contain?
H+ ions
What do alkali solutions contain?
OH- ions
How is the concentration of ions measured?
mol/dm cubed
What are H+ ions in
Water
What concentration of OH- ions do strong alkalis have?
A high one - weak alkalis have a low one
What degree of ionisation do strong acids and alkalis have?
A high one
Why is hydrochloric acid a strong acid?
Because when the HCl molecules dissolve in the water almost all of the hydrogen atoms form H+ ions (ionisation)
Why is ethanoic acid a weak acid?
Because only about 1% of the molecules form H+ ions
What are the similarities in how strong and weak acids react
- When they react with magnesium they both produce hydrogen gas
- When they react with calcium carbonate they both produce carbon dioxide gas
- In both these situations they produce the same volume of gas but the rate of reaction is faster for the strong acid
What determines concentration of acids and alkalis
The amount and proportion of water present
What volume of water do dilute acids have
A high one
Why do some metals react with acids?
Because of their position on the reactivity series
Recite the reactivity series (highest to lowest)
- Potassium
- Sodium
- Calcium
- Magnesium
- Zinc
- Iron
- Tin
- Lead
- Copper
- Silver
- Gold
How do metals at the top of the reactivity series react with acids?
Vigorously and exothermically even with dilute acids
How do metals at the bottom of the reactivity series react with acids?
Not at all
What is the general equation for metals reacting with acids?
Metal + acid = metal salt + hydrogen
What kind of salts do hydrochloric acid and metals create?
Chlorides
What is the equation for hydrochloric acid and a metal?
Metal + hydrochloric acid = magnesium chloride + hydrogen
What is the equation for sulfuric acid and a metal
Metal + sulphuric acid = metal sulfate + hydrogen
What kind of salts does sulfuric acid and a metal create?
A sulfate
What kind of salts do nitric acid and a metal create
A nitrate
What is the equation for a metal and nitric acid
Metal + nitric acid = metal nitrate + hydrogen
Define a neutralisation reaction
A chemical reaction happens if you mix together an acid and a base.
What do acids react with
Metal oxides, metal hydroxides, and metal carbonates
What are soluble bases called
Alkalis
What kind of reaction is one between an acid and a metal oxide
Exothermic (giving out heat)
What is the term for when acids react with bases or alkalis
A neutralisation reaction
How can neutralisation reactions involving acids and alkalis be characterised
HNO(3) + OH(-) = H(2)O
What is a base
A base is a substance that can neutralize the acid by reacting with hydrogen ions.
What do metal carbonates react with in a neutralisation reaction
They react with acids forming metal salts, water, and carbon dioxide gas
What is an example of a metal carbonate neutralisation reaction
Sulfuric acid + magnesium = magnesium + water + carbon dioxide
What is the test for a carbonate
To add an acid - if the substance effervesces (gives off bubbles) producing carbon dioxide gas, then it’s a carbonate (or contains the carbonate ion)
What is a titration
A method of preparing solutions of solube salts, and a way of determining the relative and actual concentrations of solutions of acids or alkalis
What is an example of an indicator used in titration
Phenolphthalein
What happens during titration
- An indicator is added to a known volume of alkali
- The acid is put into a burette
- The concentration of either the acid or alkali has to be known
- The acid is added to the alkali until the indicator changes colour
What is the equation we use to work out concentration during titration
Concentration of acid x volume of acid = concentration of alkali x volume of alkali
How do we test for a sulfate
By reacting a solution of the sulfate with a solution of barium chloride - a white precipitate of barium sulfate is formed
What is the symbol for a sulfate ion
SO(4)↑-2
What is an example of testing for a sulfate
Sodium sulfate + barium chloride = sodium chloride + barium sulfate
What kind of salt is barium sulphate
A solid insoluble salt
How can solid insoluble salts be prepared from precipitate solutions
By filtering the solution - the insoluble salt is trapped by the filter paper
What happens after the insoluble salt is separated
It is rinsed by distilled water
How can soluble salts be prepared
By reacting an acid with a metal base
What is an example of a solube salt
Magnesium sulfate
What is the result of mixing an acid and a metal base
A soluble salt, which has to be separated via evaporation
How is the excess insoluble base separated from the soluble salt?
Via filtration
How can we identify chemicals
By reacting known chemicals with them
