C3 - Quantitive Chemistry/ C4 - Chemical Changes Flashcards
What is Avogadro’s number
6.02 x 10^23
Moles equation
mass in g/Mr
How to balance equations using reacting masses
Divide mass by each Mr - find moles
Divide each mole by the smallest
If it ain a whole number, times each by the same number till whole
Put numbers in fr
concentration equation
mass/volume
(g/dm^3)
How many cm^3 is 1 dm^3
1000
How many dm^3 is 1cm^3
1/1000
acid + base
salt + water
Difference between strong and weak acids
Strong acids ionise completely in water - all acid particles dissociate to release H+ ions
Weak acids do not fully ionise in solution - Small proportion of acid particles dissociate to release H+ ions
H+ ion concentration difference (pH 4 - 6)
10^-2
Name a weak and strong acid
Ethanoic, citric and carbonic
Sulfuric, hydrochloric and nitric
Acid + Metal Oxide
Salt + Water
Acid + Metal Hydroxide
Salt + water
Acid + Metal Carbonate
Salt + Water + Carbon Dioxide
How to make an insoluble salt using an insoluble base (3 marks)
Gently warm the dilute acid using Bunsen burner - then turn off the B.B
Add the insoluble base to the acid a bit a time until no more reacts
Filter out excess solid to get salt solution
From the insoluble salt experiment how can you create crystals ( 3 marks)
Gently heat the solution using a water bath to evaporate some of the water
Then stop heating it and leave the solution to cool
Filter out crystals and dry
Acid + Metal
Salt + Hydrogen
Acid + Metal
Salt + Hydrogen
What is the conservation of mass
During a chemical reaction, no atom is lost or created
Mass of reactants is equal to mass of products
How do you show that mass is conserved in a chemical reaction
Work out rfm for both reactants and products
Explain why mass might increase in a reaction (4 marks)
One of the reactants is a gas in the air - all products are solids, liquids or aqueous
When gas reacts to form part of product
Becomes contained in reaction vessel
Total mass inside reaction vessel increases
Explain why mass might decrease in a reaction ( 4 marks)
One of the products is gas - all reactants are solids, liquids or aqueous
Before reaction, reactants are contained in the reaction vessel
If vessel isn’t enclosed, gas can escape
No longer contained in reaction vessel - total mass will decrease
How can you investigate the reactivity of different metals ( 6 marks)
Wear safety goggles
Cut metals into strips/pieces of equal surface area i.e 5cm^2
Add 20cm^3 of hcl into a test tube
Measure initial temperature ( thermometer) and record it
Add 4 pieces of each metal into different test tubes
Place a stopper on each one
After 5 minutes, using a thermometer record final temperature
Bigger the difference the more reactive the metal is
How are metal ores formed
Oxidation - gain of oxygen
Metal is oxidised to give metal oxide
How is metal extracted from an metal oxide
Reduction - loss of oxygen
Metal oxide reduced to give metal
