Acids, Alkalis and Salts Flashcards
What does concentration mean?
How much solid is dissolved in a certain volume of solution
What does dilute mean?
Relatively few particles in a given volume
What does concentrated mean?
Relatively many particles in a given volume i.e. particles much closer together
How do you convert cm^3 to dm^3?
1 dm^3 = 1000 cm^3
To convert cm^3 into dm^3, divide by 1000
What is the formula for mass concentration?
Mass concentration (g/dm^3) = Mass (g) / Volume (dm^3)
What is the formula for mole concentration?
Mole concentration (mol/dm^3) = Number of moles / Volume (dm^3)
What is the formula for the number of moles?
Number of moles = Mole concentration x Volume (dm^3)
What is the formula for mass concentration with moles?
Mass concentration = Mole concentration x Mass of one mole
What are formula for some common acids?
Nitric acid - HNO3 Hydrochloric acid - HCl Sulphuric acid - H2SO4 Phosphoric acid - H3PO4 Ethanoic acid - CH3CO2H
What is an acid?
A substance that releases H+ (aq) ions when added to water
What is a base?
A substance that reacts with acids
What are the three types of base?
Metal oxide e.g. CaO
Metal hydroxide e.g. Ca(OH)2
Metal carbonates e.g. CaCO3
What are alkalis?
Substances that release OH- (aq) ions when added to water
What is the difference between a strong and a weak acid?
In strong acids all molecules ionise and release H+ ions in water in an irreversible reaction e.g. Hydrochloric
In weak acids only a small fraction of the molecules ionise and release H+ ions in water in a reversible reaction e.g. Ethanoic
How does concentration of H+ ions affect pH?
Each time the concentration of H+ ions increases by 10 the pH decreases by 1
What is the pH at H+ concentration of 0.1 mol/dm^3?
1
What is the reaction of an acid and a metal?
Acid + metal –> Salt + hydrogen (not a neutralisation reaction)
What is the reaction of an acid and a metal oxide (base)?
Acid + metal oxide –> Salt + water
What is the reaction of an acid and a metal hydroxide (base)?
Acid + metal hydroxide –> Salt + water
What is the reaction of an acid and a metal carbonate (base)?
Acid + metal carbonate –> Salt + water + carbon dioxide
What is a titration?
An experiment that is used to find out the concentration of an unknown solution
E.g. You have a solution of unknown concentration of an alkali and an acid of known concentration. You add the acid until an indicator shows it is exactly neutralised. By using the volume of acid, concentration of acid, and volume of alkali you can calculate the concentration of alkali
How would you carry out a titration?
Wash the burette with acid and the pipette with alkali
Place a white tile under a conical flask
Fill the burette with acid. Use the pipette to fill a conical flask with a
certain volume of alkali
Add a few drops of indicator to the conical flask
Using the burette add acid to the conical flask drop by drop. Swirl the conical flask
The indicator changes colour when all the acid has been neutralised
Repeat the process to get similar results
What colour does phenolphthalein turn in acids and alkalis?
Acids - Colourless
Alkalis - Pink
What colour does methyl orange turn in acids and alkalis?
Acids - Red
Alkalis - Yellow
How would you carry out a titration calculation?
Find the number of moles of the solution you know about
Write out the equation
Work out the number of moles of the unknown substance (same if it is 1:1)
Work out the concentration of the unknown substance
How can you make soluble salts?
You can make soluble salts from:
An acid and an insoluble base (e.g. hydrochloric acid and zinc oxide make zinc chloride)
An acid and a soluble base (e.g. hydrochloric acid and sodium hydroxide make sodium chloride)
How could you prepare a soluble salt from an acid and an insoluble base?
Add the acid to a beaker
Add the solid base to the acid and stir
Warm the acid gently to allow a faster rate of reaction
Add the base until no more dissolves, ensuring all the acid has reacted
Filter to remove excess base and leave behind pure salt solution
Use crystallisation to get pure, dry crystals
How could you prepare a soluble salt from an acid and a soluble base?
Add some of the base in solution to a beaker
Add drops of indicator (not universal indicator)
Add the acid carefully using a burette
Stir
Add acid until the indicator just changes colour. Record the amount
Repeat without any indicator now you know the exact volume of acid required
Use crystallisation to get pure, dry crystals
