Chemistry Revision S4 2017

Question 1

What’s the order of the reactivity series?

Answer 1

The order of the reactivity series is:

Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Lead
Hydrogen
Copper
Silver
Gold
Platinum

Question 2

What is a displacement reaction?

Answer 2

A displacement reaction is where a more reactive metal displaces (pushes out) a less reactive compound from it’s compound.

Question 3

What is neutralisation?

Answer 3

Neutralisation is the process where an acid (PH 1-6) neutralises an alkali (PH 8-14) to form a neutralised solution (PH 7).

Question 4

What acids and alkalis measured on?

Answer 4

Acids and Alkalis are measured on a PH scale.

Question 5

What does the atomic number tell you?

Answer 5

The atomic number tells you how many protons there

are.

Question 6

Describe the structure of the atom.

Answer 6

Atoms are neutral- they have no charge overall because they have the same number of protons as electrons.

Question 7

What colour flames are produced in flame tests?

Answer 7

You can test for various metal ions by heating your substance and seeing whether it burns with a distinctive flame:

Lithium ions burn with a crimson flame.

Sodium ions burn with a yellow flame.

Potassium ions burn with a lilac flame.

Question 8

How would you carry out a flame test?

Answer 8

You can carry out a flame test by doing this scientific method:

1) Dip the wire in a acidic solution.
2) . Hold the wire in a bunsen burner flame(check to see if the wire is clean).
3) . Place some of the salt onto the wire.
4) . Hold the salt in the flame.
5) . Repeat for other salts.
6) . Record your results.
7) . Design your own table.

Question 9

What is an ion?

Answer 9

An ion is charged atom or molecule.

Question 10

Describe what an atom is.

Answer 10

All substances are made from atoms- paper in your books, the air you are breathing and every part of your body. An atom is the smallest part of an element that can exist.

Question 11

What is the atomic number?

Answer 11

The atomic number is the number of protons of electrons in the atom of that element.

Question 12

What is the atomic mass?

Answer 12

The atomic mass is the number of protons and neutrons in the atom of that element.

Question 13

Define halogens.

Answer 13

Halogens exist as diatomic molecules- that means they have two atoms in each molecule. As you go down the group, the halogens become less reactive.

Question 14

Define noble gases.

Answer 14

Noble gases are very unreliable and they exist as individual atomic molecules.

Question 15

Who was John Newlands?

Answer 15

John Newlands was an english analytical chemist in the 1800’s.

Question 16

Who was Dimitri Mendeleev?

Answer 16

Dimitri Mendeleev was a russian chemist in the 1800’s.

Question 17

How would you make salts from copper oxide?

Answer 17

You make salts using copper oxide powder by:

1). Measure 40 cm³ sulfuric acid into the 100 cm 3 beaker.
The volume does not need to be very accurate, so you can use the graduations on the beaker.

2) . Set up a tripod, a gauze and a heatproof mat. Heat the acid gently using the bunsen burner until it is almost boiling. Turn off the bunsen burner.
3) . Use the spatula to add small amounts of copper (II) oxide powder. Stir with the glass rod.

Continue to add copper (II oxide) if it keeps disappearing when stirred. When the copper (II) oxide disappears the solution is clear blue.

4). Stop adding the copper (II) oxide when some of it remains after stirring.

Allow apparatus to cool completely.

5). Set up the filter and funnel paper over the conical flask. Use the clamp stand to hold the funnel.

Filter the contents of the beaker from step 3.

6). When filtration is complete, pour the contents the conical flask into the evaporating basin.

Evaporate this gently using a water bath (250 cm³ beaker with boiling water) on a trip and gauze. Stop heating once crystals start to form.

7) . Transfer the remaining solution to the crystallising dish. Leave this in a cool place for at least 24 hours.
8) . Remove the crystals from the concentrated solution with a spatula. Gently pat the crystals dry between two pieces of filter paper.

These are pure dry crystals of copper (II) sulphate.

Question 18

How do you electrolyse copper sulphate?

Answer 18

You electrolyse copper sulphate by:

1) . Pour copper (II) chloride solution into the beaker to about 50 cm³.
2) . Add the lid and insert carbon rods through the holes. The rods must not touch each other.

Attach crocodile leads to the rods. Connect the rods to the dc (red and black) terminals of a low voltage power supply.

3) . Select 4 V on the power supply and switch on.
4) . Look at both electrodes. Is there bubbling at neither, one or both electrodes?
5) . Use tweezers to hold a piece of blue litmus paper in the solution next to the positive electrode (the one connected to the red terminal). You will need to lift the lid temporarily to do this.

Write your observations in the first blank row of the table. What is the element?

6). After, no more than five minutes, switch off the power supply.

Examine the negative electrode (the one connected to the black terminal). Is there evidence of a metal coating on it? What could it be?

Record your results in the table.

7). Clean the equipment carefully.

Repeat steps 1-6 using solutions of:

1) . Copper (II) sulfate
2) . Sodium chloride.
3) . Sodium sulfate.

Question 19

What properties do group 1 (alkali metals) have in the periodic table?

Answer 19

Group 1 metals have different properties to transition metals:

1) . Group 1 metals are much more reactive than transition metals - they react more vigorously with water, oxygen, or Group 7 elements, for example.
2) . They’re also much less dense, strong and hard than the transition metals. and have much lower melting points (the exception to this is the transition metal mercury, which is a liquid at room temperature).

Question 20

What does covalent bonding mean?

Answer 20

Covalent bonding is where atoms share electrons with each other so that they’ve got full outer shells.

Question 21

What is the method for neutralisation?

Answer 21

The method for neutralisation is:

1) . Use the pipette to measure 25cm³ of alkali into a conical flask.
2) . Stand the conical flask on a white tile.
3) . Fill the burette with acid using a funnel
4) . Record the initial reading of acid in the burette
5) . Add a small amount of indicator (e.g phenolphthalein, methyl orange, or litmus) to the conical flask
6) . Slowly open the burette tap while swirling the conical flask
7) . Add acid drop-by- drop near the endpoint
8) . Close the burette when a colour change occurs in the indicator (phenolphthalein [pink → colourless], methyl orange [yellow → red], litmus [blue → red])
9) . Record the final reading of acid in the burette and calculate the titre
10) Repeat until you have two concordant results (within 0.1 cm³ of each other).

Question 22

Give me the scientific method of how to carry out temperature changes.

Answer 22

You would do this required practical by:

1) . Measure 25cm³ of acid into a polystyrene cup.
2) . Stand the cup inside the beaker (this will make it more stable).
3) . Measure and record the temperature of an acid
4) . Measure 5cm³ of alkali and add it to the polystyrene cup.
5) . Put a lid on the cup and gently stir the solution with the thermometer through the hole in the lid
6) . When the reading on the thermometer stops changing, record the temperature.
7) . Repeat steps 4-5 to add further 5cm³ amounts of alkali to the cup. A total of 40cm³ needs to be added
8) . Repeat steps 1-7
9) . Calculate the mean maximum temperature reached for each of the sodium hydroxide volumes.

Question 23

How would you observe colour change in rates of reaction?

Answer 23

You would observe colour change in rates of reaction by doing this scientific method:

1) .Measure 10 cm³ sodium thiosulfate solution into the conical flask.
2) . Measure 40 cm³ of water and add it to the flask
3) . Put the conical flask on the black cross
4) . Measure 10 cm³ of dilute hydrochloric acid
5) . Add the acid to the flask. At the same time, swirl the flask gently and start the stop clock.
6) .Look down though the top of the flask. Stop the clock when you can no longer see the cross and record the time taken
7) . Repeat steps 1-6 four times, using different volumes of sodium thiosulfate and water. This will change the concentration of sodium thiosulfate.
8) . Repeat steps 1-7 twice more
9) . Calculate the mean time for each of the sodium thiosulfate concentration.

Question 24

Give me the required practical for chromatography.

Answer 24

You would carry out chromatography by using this scientific method:

1) .Draw a horizontal pencil line 2 cm from the a short edge of the chromatography paper. Mark pencil spots at equal intervals across the line. Keep at least 1 cm away from each end.
2) . Use a glass capillary tube to put a small spot of each colouring on the pencil spots. Label each spot in pencil
3) . Pour water into the beaker to a depth of no more than 1 cm
4) . Suspend the paper in the beaker so that the bottom edge of the paper dips in the water.
5) . Wait for the water solvent to travel at least three quarters of the way up the paper. Remove the paper draw another pencil line on the dry part of the paper as close to the wet edge as possible.
6) . Hang the paper up to dry throughly
7) . Calculate the Rf values for each spot.