Topic 4- Acids and Alkalis Flashcards
State all the general equations:
Base + acid = salt + water ( BASHOj
Alkali + acid= salt + water
Metal + acid = salt + hydrogen
Metal carbonate + acid = salt + water + carbon dioxide (CASHOCO)
What is an acid and why is HCL and acid?
An acid is a substance which produces hydrogen ions (H +) when dissolved in solution.
HCL dissolves in water to produce hydrogen ions.
What is a base?
Substances that can react with acids and neutralise them to make a salt and water are called bases. They are usually metal oxides or metal hydroxides. For example, copper oxide and sodium hydroxide are bases.
They can be alkalis.
What is an Alkali and why is NaOH and alkali?
A substance which produces hydroxide ions (OH-) when dissolved in water. This is a soluble base.
NaOH is an alkali because because it dissolves in water to produce hydroxide ions (OH-)
What is meant by neutralisation?
Write an ionic equation showing the neutralisation of an acid with an alkali to make water.
This is when the hydrogen ions H+ of an acid react with and are cancelled out by hydroxide ions (OH-) from an alkali or by other substances.
Ionic equation:
H+ + OH- —> H2O
Describe the difference between a strong acid and a weak acid:
In a strong acid all the acid splits into ions when dissolved in water to give a high concentration of H+ ions. Low pH
In a weak acid some of the acid splits into ions she dissolved in water. This gives a lower concentration of H+ ions and a higher pH.
Overall the difference is strong acids like hydrochloric acid fully dissociate from H+ ions where as weak acids like ethanoic acids do not.
What is the equation for calculating concentration and what are the units for it?
Concentration = amount of substance/volume
And the unit for this is g/dm 3
Name three indicators and their colours in acid and alkali?
Universal indicator- acid:red alkali:blue
Litmus- acid:red Alkali:blue
Phenolphthalein- acid:red Alkali:blue
Acids containing hydrogen ions are:
Hydrochloric acid- HCL
Sulphuric acid- H2SO4
Nitric acid- HNO3
What is the concentration of a solution?
This is the number of particles per unit volume.
Alkalis containing hydroxide ions?
Sodium hydroxide- NaOH
Potassium hydroxide- KOH
Calcium hydroxide- Ca(OH)2
What is the difference between strong acids and concentrated acids.
In a strong acid the hydrogen ions are fully dissociated in solution whereas a concentrated acid is a substance less than 7 which has not had much water added to it.
The strength tells you the what proportion of the acid molecules ionise in water the concentration measures how much acid there is in a litre (1dm3) of water.
What is a salt?
An ionic substance consisting of metals and non metals.
Making insoluble salts from 2 solutions (precipitate reaction)
A precipitate reaction occurs when 2 soluble solutions are addd together to give an insoluble product.
Method:
1) add 1 spatulas of lead nitrate to test tube. Add water to dissolve it. Water should be deionised.
2) shake it thoroughly to make sure all lead nitrate is dissolved and do the same to sodium chloride.
3) Tip the 2 solutions into a small beaker and stir to mix it together. The lead chloride should precipitate out.
4) put filter paper into filter and and stick funnel in conical flask.
5) pour contents of beaker into filter paper. The solution is now soluble sodium nitrate and the solid lead chloride can be scraped of filter paper.
Making soluble salts using an acid and an insoluble base.
Add an excess of the insoluble base to some acid.
Heat the mixture to speed up the reaction.
Filter of the unreacted base using filter paper and a funnel.
Collect filtrate and crystallise out the salt by evaporation.
Dry crystals in an oven.
