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AQA GCSE Chemistry > RPAs > Flashcards

RPAs Flashcards

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1
Q

What does repeatable mean?

A

Whether the original person can get the same results when redoing the same method.

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2
Q

What does reproducible mean?

A

Whether a different person can get the same results when redoing the same method.

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3
Q

What does precise mean?

A

If the experiment results are close to the mean.

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4
Q

What does accurate mean?

A

If the experiment results are close to the true value.

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5
Q

What is an independent variable?

A

The variable that is changed throughout the experiment.

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6
Q

What is a dependant variable?

A

The variable that is being measured throughout the experiment.

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7
Q

What is a control variable?

A

The variables that are kept the same throughout the experiment.

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8
Q

RPA 1: Making Soluble Salts
Describe the 10-step method of this practical.

A
  1. Pour 20 cm^3 of dilute sulfuric acid into a beaker.
    (This is the limiting reagent.)
  2. Heat the acid until it’s almost boiling.
  3. Use a spatula to add copper oxide to the acid.
    (The copper oxide will react and seem to disappear as it is stirred.)
  4. Stop adding copper oxide if some remains after stirring.
    (The reaction has stopped as all the acid has reacted.)
  5. Use filtration to remove the unreacted copper oxide.
  6. Place the solution in an evaporating basin and heat gently over a beaker of boiling water.
  7. Heat until half the solution remains.
  8. Leave solution for 24 hours in a cool place for crystals to form.
  9. Scrape crystals onto paper towel and pat them dry.
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9
Q

RPA 1: Making Soluble Salts
What is the equation for the making of salts in this practical?

A

Sulfuric Acid + Copper Oxide > Copper Sulfate + Water.

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10
Q

RPA 1: Making Salts
What are the 3 safety precautions needed for this practical?

A
  • Wear goggles as sulphuric acid is corrosive.
  • Make sure hair is tied back.
  • When the Bunsen burner is not in use, turn it off or leave it on the orange safety flame.
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11
Q

RPA 2: Titration
Describe the 13-step method of this practical.

A
  1. Use the pipette to measure 25cm^3 of sodium hydroxide into the conical flask.
  2. Place the conical flask on a white tile.
  3. Fill the burette with sulphuric acid using a funnel.
  4. Record the initial reading of acid in the burette.
  5. Add a 5 drops of indicator 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.
    (The solution turns from pink to colourless.)
  9. Record the final reading of acid in the burette and calculate the titre. This is the volume of acid used to neutralise the alkali.
  10. Present results in a table and calculate the mean.
  11. Calculate the number of moles of sodium hydroxide used in the titration.
  12. In the balanced equation the ratio between sodium hydroxide and sulphuric acid is 2:1.
    Therefore to find out the moles of sulphuric acid divide the moles of sodium hydroxide by 2.
  13. Use the formula [concentration= moles/volume (mean titre volume)] to work out the concentration of sulphuric acid.
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12
Q

RPA 2: Titration
What is the equation for the titration in this practical?

A

Sulfuric Acid + Sodium Hydroxide > Sodium Sulfate + Water.

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13
Q

RPA 2: Titration
What are the safety precautions needed for this practical?

A
  • Wear goggles when working with acids.
  • Tie hair back.
  • Report any broken glassware immediately.
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14
Q

RPA 2: Titration
What is the aim of this investigation?

A

To find the concentration of a dilute sulfuric acid solution.

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15
Q

RPA 3: Electrolysis
Describe the 8-step method of this practical.

A
  1. Add about 50cm^3 of copper chloride solution to a beaker.
  2. Add the lid and insert electrodes through the holes making sure the electrodes don’t touch.
  3. Attach crocodile leads to the electrode and connect the rods to the DC terminals of a low voltage power supply.
  4. Set the power supply to 4V and switch the power supply on.
  5. Using the forceps hold the litmus paper near the positive electrode.
  6. After a few minutes turn the power supply off and observe the negative electrode.
  7. Record observations at the electrodes.
  8. Repeat with sodium chloride.
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16
Q

RPA 3: Electrolysis
What are the equations for the electrolysis in this practical?

A

Hydrogen gas formed at the negative electrode.
Hydrogen + 2 Electrons > Hydrogen
2H+(aq) + 2e- → H2(g)

Oxygen gas formed at the positive electrode.
Hydroxide > Water + Oxygen + 4 Electrons
4OH-(aq) → 2H2O(l) + O2(g) + 4e-

17
Q

RPA 3: Electrolysis
What are the safety precautions needed for this practical?

A
  • Safety goggles must be worn.
  • Room should be well ventilated because large quantities of chlorine gas is toxic.
18
Q

RPA 3: Electrolysis
What is the aim of this investigation?

A

Investigate what happens when aqueous solutions are electrolysed using unreactive electrodes.

19
Q

RPA 3: Electrolysis
What were the 2 results of this investigation at the anode?

A
  1. Copper Chloride formed chlorine gas - seen as bubbles of gas and litmus paper was bleached white by it.
  2. Sodium Chloride also formed chlorine gas.
20
Q

RPA 3: Electrolysis
What were the 2 results of this investigation at the cathode?

A
  1. Copper Chloride formed solid copper - seen as a brown/red coating on the cathode rod.
  2. Sodium Chloride formed hydrogen gas, seen as bubbles of gas being produced more rapidly.
21
Q

RPA 4: Temperature Changes
What is the aim of this investigation?

A

To investigate the variables that affect temperature change in chemical reactions.

22
Q

RPA 4: Temperature Changes
Describe the 9-step method of this practical.

A
  1. Measure 25cm^3 of hydrochloric acid into a polystyrene cup.
  2. Place the cup inside the beaker to make it more stable.
  3. Measure and record the temperature of the hydrochloric acid.
  4. Measure 5cm^3 of sodium hydroxide and add it to the cup.
  5. Quickly put a lid on the cup and gently stir the solution with the thermometer through the hole of lid.
  6. When the reading on the thermometer stops changing and becomes fairly constant, record the temperature.
  7. Repeat steps 4 and 5 to add further 5 cm^3 amounts of sodium hydroxide to the cup. A minimum total of 40 cm3 needs to be added.
  8. Repeat steps 1–7 to ensure reliability of results.
  9. Calculate the mean maximum temperature reached for each of the sodium hydroxide volumes.
23
Q

RPA 4: Temperature Changes
What are the safety precautions needed for this practical?

A

-Wear goggles.

24
Q

What are the RPAs that could appear in paper 1?

A

RPA 1: Making Soluble Salts
RPA 2: Titration
RPA 3: Electrolysis
RPA 4: Temperature Changes

AQA GCSE Chemistry (11 decks)

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