PAG 12 - Research Skills

Question 1

What’s a prediction using scientific knowledge called

Answer 1

Hypothesis

Question 2

What’s meant by accuracy

Answer 2

How close measurement is to true value

Question 3

What are variables

Answer 3

Factors that can affect outcome of experiment

Question 4

What’s an independent variable

Answer 4

Factor that’s changed during experiment to see effect it has on another factor

Question 5

What’s a dependent variable

Answer 5

Factor that’s measured/observed in experiment

Question 6

What’s a control variable

Answer 6

Factor that’s kept constant throughout experiment

Question 7

What’s oxidation

Answer 7

Loss of electrons/increase in oxidation state

Question 8

What’s reduction

Answer 8

Gain of electrons

Decrease in oxidation state

Question 9

What’s redox reaction

Answer 9

A reaction in which some atoms are oxidised and others are reduced

Question 10

How can % of Fe in Fe tablet be found

Answer 10

1. Prepare a standard solution of iron (Il) using the tablets and sulfuric acid
2. Titrate a set volume of this iron(Il) solution against a solution of KMnO4
3. Repeat until you obtain concordant results and calculate a mean titre
4. Calculate the number of moles of KMnO, that reacted
5. Use the ratio in the chemical equation to calculate the number of moles of
   iron that reacted
6. Calculate the percentage mass of iron using the mass present in the standard solution

Question 11

Describe how to make standard solution of acidified iron(II) sulfate

Answer 11

1. Grind up some iron tablets. Measure the total mass of the iron tablets in a weighing boat.
2. Add the powdered tablets to a conical flask and reweigh the weighing boat. The difference between the masses is the mass of iron tablets in the solution.
3. Add a 50cm’ of sulfuric acid to the conical flask to dissolve the iron. Stopper the flask and shake well. Leave the flask for the residue to settle.
4. Filter the solution into a volumetric flask without disturbing the residue. Rinse the filter paper with a small volume of distilled water.
5. Fill the volumetric flask up to the graduation mark with sulfuric acid then stopper
   and invert the flask to mix.

Question 12

Write equations for redox reaction between Fe^2+ and manganite ions

Answer 12

5Fe^2+ + MnO4^- + 8H+ —>
5Fe^3+ + Mn^2+ + 4H2O

Question 13

When making a standard solution, what method should be used to find mass of solute

Answer 13

Weighing-by-difference method

Question 14

Why is an indicator not required in titration between Fe^2+ and MnO4^-

Answer 14

KMnO4 is self indicating

End point is when you get the 1st permanent pink colour

Question 15

In titration, what are concordant results

Answer 15

Titres that are within 0.1cm^3 of each other

Question 16

Give 3 possible sources of error in this experiment

Answer 16

• The iron may not completely dissolve - warming
  may help
• Some iron may not be transferred between containers - take washings
• The end point may be hard to see - place a white tile underneath the conical flask to make the colour change easier to observe

Question 17

What’s primary research

Answer 17

New set of data has been collected

Conclusions are drawn from this new data

Question 18

2 examples of primary research

Answer 18

Surveys

Experiments

Question 19

What’s secondary research

Answer 19

Data from other studies that are used to draw conclusions

Question 20

Whats the difference between qualitative and quantitative data

Answer 20

Qualitative = descriptions of observations

Quantitative = numerical data

Question 21

Online and offline resources can be used for what

Answer 21

Research