C5 How Much? Flashcards
What is the PH of a weak acid
4–6
What is the PH of a strong acid
1–2
What does the strength of an acid tell you?
Tells you what proportion of acid molecules ionise in water
How do you make an insoluble salt?
To make an insoluble salt you need ions which are in a solutions so that they can move about
What is the equation to work out number of moles?
Mr
What is a mole?
The relative atomic mass of an element is the average mass of an atom compare to the mass of an atom of carbon 12
Uses of a gas syringe in measuring gas volumes
1) might blow plunger off
2) Collects most gases
3) to the nearest centimetre cubed
Uses of an upturned measuring cylinder in gas volumes
1) Bubbles gas
2) no good for hydrogen/chloride/ammonia as they dissolve in water
What is electrolysis
The breaking down of a substance with electricity
What is the equation at the anode?
4OH- - 4e- >O2 + 2H2O
What is the equation at the Cathode?
2H+ + 2e- > H2
How can you increase the amount of substance produced at electrolysis?
If you increase the amount of electrons, you increase the amount of substance produced
How too calculate empirical formula ?
1) List all elements
2) Write there in experimental masses/percentage
3) divide each mass/percentage by the Ar
4) Turn numbers into a ratio
5) get the ratio into simplest form
What does it mean if mass is conserved in a chemical reaction
This means that the mass of reactants is equal to mass of products
What is empirical formula
Empirical formulas give the smallest whole number ratio of atoms in a compound
1 dm cubed
Is 1000 cm³ (litre)
Name the two calculations to work out concentration
concentration X volume
Number of moles X Mr
How do you make solution more concentrated
The more solute you dissolve in a given volume, The more crowded the molecules are and the more concentrated solution
What is a precipitation reaction?
To solutions reacting together to make an insoluble substance
This makes the solution turn cloudy/murky
What does equilibrium do?
It will move in the opposite way to balance the chemical reaction
What is the contact process used for?
To make sulphuric acid
How do you make sulphuric acid in the contact process?
First burn sulphur in air (S + O2 > SO2)
Then oxidise to 2SO2 (2SO2 + O2 <> 2SO3
Add water to sulphur trioxide to make sulphuric acid ( SO3 + H2O > H2SO4)
What is the equation for neutralisation?
Acid + alkali = salt + water
