Practicals

Question 1

How could you investigate the solubility of solids in water at diff temps?

Answer 1

-Place a beaker containing 100cm³ of water in a water bath
-Add known masses of solid to the beaker until the solution is saturated
-Filter the solution to remove undissolved solid
-Record the mass of solid and evaporating basin and calculate the mass of solute that dissolved
-Repeat at diff temps

Question 2

When investigating how long it takes for a solid to dissolve in water, what would you expect when the temperature of the water increases? Why?

Answer 2

-Temp of the water increases, time takem for a given mass of solid decreases- solubility increases.

Question 3

How is the solubilty of a gas affected by temperature?

Answer 3

As temperature increases, gases become less soluble

Question 4

How can chromatography show the composition of a mixture?

Answer 4

Different coloured substances in the mixture will separate as they have different solubilities in the solvent and will travel at different rates.

Question 5

How does paper chromatography work to separate a mixture?

Answer 5

-Mobile phase moves through the stationary phase so anything dissolved in the mobile phase will move with it
-Compounds interact diff with each phase so will move diff distances through the stationary phase and will be separated

Question 6

Calculate Pf value

Answer 6

Distance travelled by substance / Distance travelled by solvent

Question 7

Describe how to find the mass of a metal oxide by combustion

Answer 7

-Measure the mass of the metal solid
-Place the solid in the crucible on a tripod over a bunsen burner
-Heat, lifting the lid of the crucible regularly
-Reweigh the mass of the solid and repeat the heating and mass measurement until there is no further decrease in mass
-Record the mass of oxide formed

Question 8

Metal oxides can be produced by heating metals in a crucible. Why must a lid be used and why should it be regularly lifted?

Answer 8

-A lid prevents the metal oxide product escaping
-The lid should be regularly lifted to allow oxygen into the reaction.

Question 9

Describe how to find the formula of the metal oxide by combustion

Answer 9

-Find the initial mass of the solid metal
-Find the mass of oxygen used in the reaction by calculating the increase in mass when the oxide is formed
-Divide the masses of metal and oxygen by their molecular masses
-This provides a ratio of metal to oxygen, giving the empirical formula of the metal oxide.

Question 10

How to set up a general electrolysis experiment

Answer 10

-Place the positive and negative electrodes in a beaker containing a molten or dissolved ionic compound
-Connect both electrodes to a power supply with wires

Question 11

How do you investigate what happens when an aqueous solution of NaCl is electrolysed?

Answer 11

-Half fill a beaker with aqueous NaCl
-Place a lid on the beaker and insert the electrodes into the solution through holes in the lid
-Connect the electrodes to a low voltage power supply
-Switch the power supply to 4V
-Turn off the power after a few minutes and record any observations

Question 12

What forms at the cathode and the anode in electrolysis?

Answer 12

Cathode: Metals or Hydrogen
Anode: Non-Metals

Question 13

In the electrolysis of NaCl hydrogen is produced a the cathode. Why is sodium not produced?

Answer 13

Hydrogen is produced because sodium is more reactive than hydrogen. Sodium remains in the solution.

Question 14

At which electrode does oxidation occur?

Answer 14

Positive electrode (anode)

Question 15

To which electrode do positive ions move towards?

Answer 15

Negative electrode (cathode)

Question 16

What are the percentages of the four most abundant gases in air?

Answer 16

Nitrogen 78%
Oxygen 21%
Argon 0.9%
Carbon dioxide 0.03%

Question 17

How could you approximate the percentage by volume of oxygen in air using a metal?

Answer 17

-Place wet iron fillings inside the ened of a burette
-Stand the burette vertically over a trough of water using a clamp
-Record the starting heigh of the water in the burette
-After a few weeks record the final height of the water in the burette
-Calculate the % of oxygen in air using the change in volume compared to the original column of air in the burette

Question 18

How could you approximate the percentage by volume of oxygen in air using a non-metal?

Answer 18

-Float an evaporating dish of phosphorus in a trough of water
-Ignite the phosphorous
-Place a bell jar into the water trough, covering the dish
-Record the starting heigh of the water level in the bell jar
-Leave the apparatus for a few days
-Measure the final water level in the ell jar
-The decrease in the volume of air is the volume of oxygen originally in jar
-Calculate the % of oxygen in air using the change in volume compared to the original value.

Question 19

WHen approximating the percentage by volume of oxygen in air using a non-metal, why does the water level in the bell jar rise?

Answer 19

Combustion of the non-metal uses up oxygen so the water level rises to replace the volume of oxygen used up.

Question 20

What is the type of reaction that occurs when a metal reacts with an acid? Why does this reaction occur?

Answer 20

Displacement reaction. Metal is more reactive than hydrogen, so it will displace hydrogen and combine with the chloride or sulfate ion

Question 21

Why will metals lower than hydrogen in the reactivity series not react with dilute hydrochloric or sulfuric acid?

Answer 21

They are less reactive than hydrogen so are unable to displace hydrogen from acid to form a salt

Question 22

Obsevations for a metal + acid reaction

Answer 22

-Bubbles of gas
-Dissapearance of metal
-Possible colourless solution
-Temp increase

Question 23

How would you prepare a sample of pure, dry copper sulfate crystals from a sample of insoluble copper oxide?

Answer 23

-React warm sulfric acid with excess copper oxide
-Filter to remove the excess copper oxide
-Heat the solution to start evaporation
-Turn off the heat and leave until all the water has evaporated
-Left with copper sulfate crystals

Question 24

Why should the copper oxide be added to the sulfuric acid in excess?

Answer 24

-Ensure all the acid reacts
-Excess copper oxide can easily be removed by filtration bc its insoluble

Question 25

Why shpuld you warm an acid?

Answer 25

React faster and helps make sure it all reacts

Question 26

How can an insoluble salt be prepared from 2 soluble reactants

Answer 26

-Mix the reactants with a solvent in a beaker
-POwer the solution through a runner with filter paper into a beaker, product remains on the filter paper
-Rinse the insoluble products with excess solvent and dry.

Question 27

When preparing Lead (II) sulfate, why is it important that the reactants are mixed once combined?

Answer 27

To ensure a complete reaction

Question 28

Describe an experiment to measure the temp change of a of a combustion reaction?

Answer 28

-Put 100 cm³ of water in a copper can and record its temp
-Measure the mass of a spirit burner filled with the substance being tested then place it below the copper can and light the wick
-Continue heating until the spirit burner is extinguished.
-Measure the final mass of the spirit burner and the maximum temp of the water

Question 29

In a neutralisation reaction what steps can be taken to ensure minimal heat loss in the reaction?

Answer 29

-Polysterene cup
-Place an insulated lid on the cup
-Place polystyrene cup in a beaker filled with cotton wool

Question 30

How can you measure the rate of reaction between HCl and marble chips?

Answer 30

-Add reactants to a conical flask
-Immediately attach a gas syringe or upside down measuring cylinder filler with water to the conical flask using a bung and capillary tube.
-Take regular recordings of time and the volume of gas produced
-Rate=volume of gas produced/time

Question 31

How could you increase the surface area of marble chips?

Answer 31

Turn the chips into a powder by grinding them down

Question 32

How could you decrease the concentration of a sample of hydrochloric acid?

Answer 32

Add a known volume of deionised water

Question 33

How can the rate of a reaction be measured? 3 ways

Answer 33

-Measure change in mass
-Measure volume of gas produced
-Observe colour change/precipitate formed

Question 34

4 ways in which the rar can be increased?

Answer 34

-Increase sa of reactants
-Use a catalyst
-Increase temp
-Increase pressure/conc

Question 35

How does conc of reactants affect the ror?

Answer 35

Increase. Increases the ror because there are more particles in the same volume so more successful

Question 36

How does the surface area of reactants affect the rate of reaction?

Answer 36

Increases. More particles exposed so more frequent successful collisions.

Question 37

How to calculate the ror

Answer 37

amount of product formed or reactant used / Time

Question 38

How does a catalyst increase the ror

Answer 38

Provides an alternative pathway which has a lower activation energy. More collisions will exceed activation energy so more frequent successful collisions

Question 39

WHich 3 reagents are required to prepare ethyl ethanoate?

Answer 39

-Ethanoic acid
-Ethanol
-Sulfurc acid (catalyst)

Question 40

What technique is used to produce an ester from a carboxylic acid and an alcohol?

Answer 40

Distillation

Question 41

How can acids be removed from the impure ester?

Answer 41

Add sodium carbonate until the mixture stops fizzing

Question 42

How can ethanol be removed from an impure ester?

Answer 42

Calcium chloride

Question 43

Hwta property of esters allows them to be collected by distillation?

Answer 43

Low boiling points