C3 - Quantitive Chemistry/ C4 - Chemical Changes

Question 1

What is Avogadro’s number

Answer 1

6.02 x 10^23

Question 2

Moles equation

Answer 2

mass in g/Mr

Question 3

How to balance equations using reacting masses

Answer 3

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

Question 4

concentration equation

Answer 4

mass/volume
(g/dm^3)

Question 5

How many cm^3 is 1 dm^3

Answer 5

1000

Question 6

How many dm^3 is 1cm^3

Answer 6

1/1000

Question 7

acid + base

Answer 7

salt + water

Question 8

Difference between strong and weak acids

Answer 8

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

Question 9

H+ ion concentration difference (pH 4 - 6)

Answer 9

10^-2

Question 10

Name a weak and strong acid

Answer 10

Ethanoic, citric and carbonic
Sulfuric, hydrochloric and nitric

Question 11

Acid + Metal Oxide

Answer 11

Salt + Water

Question 12

Acid + Metal Hydroxide

Answer 12

Salt + water

Question 13

Acid + Metal Carbonate

Answer 13

Salt + Water + Carbon Dioxide

Question 14

How to make an insoluble salt using an insoluble base (3 marks)

Answer 14

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

Question 15

From the insoluble salt experiment how can you create crystals ( 3 marks)

Answer 15

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

Question 16

Acid + Metal

Answer 16

Salt + Hydrogen

Question 17

Acid + Metal

Answer 17

Salt + Hydrogen

Question 18

What is the conservation of mass

Answer 18

During a chemical reaction, no atom is lost or created
Mass of reactants is equal to mass of products

Question 19

How do you show that mass is conserved in a chemical reaction

Answer 19

Work out rfm for both reactants and products

Question 20

Explain why mass might increase in a reaction (4 marks)

Answer 20

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

Question 21

Explain why mass might decrease in a reaction ( 4 marks)

Answer 21

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

Question 22

How can you investigate the reactivity of different metals ( 6 marks)

Answer 22

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

Question 23

How are metal ores formed

Answer 23

Oxidation - gain of oxygen
Metal is oxidised to give metal oxide

Question 24

How is metal extracted from an metal oxide

Answer 24

Reduction - loss of oxygen
Metal oxide reduced to give metal

Question 25

When working out Mr do you ignore the big number or small number

Answer 25

BIG NUMBA!