acids and alkalis Flashcards
(31 cards)
Define acid in terms of pH
A substance with a pH of less than 7.
Define acids in terms of ions
A substance which releases H+ ions in solution.
What does (aq) stand for?
Aqueous: when something is dissolved in water.
E.g. NaCl(aq) is salt water.
State the three common acids and give their formulae
Hydrochloric acid, HCl(aq); Sulphuric acid, H2SO4(aq); Nitric acid, HNO3.
Which ions do the common acids form in solution?
HCl forms H+ and Cl-, H2SO4 forms 2H+ and SO4^2-, HNO3 forms H+ and NO3-.
What is a neutral solution?
A solution with a pH of 7. Water is an example.
How do you measure pH?
With an indicator or pH probe.
What is a base?
A metal oxide, hydroxide or carbonate that will react with an acid.
E.g. copper oxide.
What is an alkali?
A soluble base.
E.g. sodium hydroxide.
Which ions are always present in a solution of an alkali?
OH-.
What is a salt?
A compound formed when some or all of the hydrogen from an acid is replaced by a metal.
E.g. CuSO4, copper sulphate, where copper has replaced H from H2SO4.
What type of salts are formed by the three main acids?
Hydrochloric acid produces chlorides, sulphuric acid produces sulphates, nitric acid produces nitrates.
What is a neutralisation reaction?
A reaction involving an acid that results in a neutral solution.
Which ions always react together in a neutralization reaction between acids and alkalis?
H+ and OH-.
Write the equation showing the reaction between H+ and OH- ions
H+ + OH- → H2O.
How do you make a soluble salt from an acid?
React the acid with a base.
E.g. to make copper sulphate, react copper oxide with sulphuric acid.
If a salt is in solution, how do you extract it as a solid?
Allow the water to evaporate off and it will leave the salt behind as a solid.
What is a strong acid?
An acid which completely ionises in water.
E.g. when HCl is in water, all the HCl molecules split up into H+ and Cl-.
What is a weak acid?
An acid where not all the molecules ionise.
E.g. ethanoic acid.
What is the relationship between the strength of an acid and its pH?
As an acid increases in strength, the pH decreases.
What is a concentrated acid?
An acid where there are lots of acid particles in the water.
What is a dilute acid?
An acid where there are fewer acid particles in the water.
How is pH measured?
pH is related to the concentration of H+ in a solution.
Why would a scientist carry out a titration?
To determine the volume of acid/alkali needed to neutralise the acid/alkali.
