Headstart

Question 1

Accuracy

Answer 1

How close a measured value is to the true value of the quantity being measured

Question 2

Precision

Answer 2

How close two or more measurements are to each other.

Question 3

Repeatability

Answer 3

How closely two successive measurements of the same quantity match, when carried out under the same conditions of measurement (observer, procedure, instrument, location).

Question 4

Reproducibility

Answer 4

How closely two measurements of the same quantity match, when carried out under changed conditions of measurement (observer, procedure, instrument, location)

Question 5

Resolution

Answer 5

The smallest change in the quantity being measured that results in a perceptible change on the measuring instrument. For example, the resolution of a burette is 0.05 mL.

Question 6

Validity

Answer 6

The extent to which an experiment investigates what it aims or claims to investigate. This is affected by both experimental design (eg controlled variables) and how it is conducted (eg observer bias).

Question 7

Random Errors

Answer 7

Unpredictable variations in the measurement process resulting in a spread of readings. Eg subjective human judgement

Question 8

Systematic Errors

Answer 8

Systematic Errors cause inaccuracy in a systematic manner so that when a value is measured repeatedly, the error is the same. Eg incorrectly calibrated instruments or parallax error.

Question 9

Rules for Significant Figures (in Chemistry)

Answer 9

All digits where a number is expressed in standard form. For other numbers, all digits between the first non-zero digit and the final digit including trailing zeros. Whole numbers without a decimal point have the same number of sig-figs as digits in the number.

Question 10

Outliers

Answer 10

Data points or observations that differ significantly from other data points or observations. These may be caused by mistakes (and therefore omitted) but should be accounted for before omission as an ethical approach to dealing with data.

Question 11

Steps for stoichiometry problems

Answer 11

1. Calculate the number of moles of ‘known’ (or limiting reagent, where applicable)
2. Use the molar ratio to determine the number of moles of ‘unknown’
3. Answer the question with appropriate sig figs and units.

Question 12

How to calculate % (w/v)

Answer 12

Determine the mass in grams of the solute that would be present in 100 mL of the solution

Question 13

How to use the ideal gas equation to calculate volume in L

Answer 13

V = nRT/P

Question 14

How to use the ideal gas equation to calculate pressure in kPa

Answer 14

P = nRT/V

Question 15

How to use the ideal gas equation to calculate moles

Answer 15

n = PV/RT

Question 16

How to use the ideal gas equation to calculate temperature in Kelvin

Answer 16

T = PV/nR

Question 17

Standard conditions

Answer 17

25 degrees celsius and 100kPa

Question 18

Units in the ideal gas equation (except R)

Answer 18

Pressure in kPa, Volume in L, Amount in moles, Temperature in Kelvin

Question 19

Evidence for oxidation

Answer 19

Loss of electrons; Increase in oxidation number; gain of oxygen (except F); loss of hydrogen (eg organic molecules)

Question 20

Evidence for reduction

Answer 20

Gain of electrons; decrease in oxidation number; loss of oxygen (except F); gain of hydrogen (eg organic molecules)

Question 21

What happens to the oxidant (oxidising agent) in a redox reaction

Answer 21

It is reduced

Question 22

What happens to the reductant (reducing agent) in a redox reaction?

Answer 22

It is oxidised

Question 23

What is the site of oxidation?

Answer 23

The Anode

Question 24

What is the site of reduction?

Answer 24

The Cathode

Question 25

What is always present at the cathode?

Answer 25

The oxidant

Question 26

What is always present at the anode?

Answer 26

The reductant

Question 27

Steps for balancing a half equation

Answer 27

1. Balance the Key Element (changes oxidation number) 2. Balance Oxygen using water 3. Balance Hydrogen using H+ 4. Balance charge using electrons 5. Add state symbols

Question 28

Reliability

Answer 28

How consistently an experiment is able to produce consistent results even when conditions are varied (observer, procedure, instrument, location)

Question 29

Equivalence Point

Answer 29

The point in a titration when the solutions have reacted in the exact mole ratio as shown by the reaction equation - neither is in excess. (in fact neither reactant is present at all - only products!)

Question 30

End Point

Answer 30

The point in a titration where an observation (eg colour change of the indicator) signals the end of the titration itself. Good experimental design will ensure that the end point is near the equivalence point in terms of volume of titrant delivered.

Question 31

Total range of concordant titres

Answer 31

Up to 0.10 mL

Question 32

Which of these is a correctly shown titre value? 10.59 mL, 10.55 mL, 10.4 mL

Answer 32

10.55 mL (2 decimal places with the second being 0 or 5)

Question 33

What should you rinse a burette with?

Answer 33

The solution to be used in the burette (titrant). Rinsing with water would dilute the titrant.

Question 34

What should you rinse a volumetric pipette with?

Answer 34

The solution to be used in the volumetric pipette (analyte). Rinsing with water would reduce the amount of analyte delivered in the aliquot.

Question 35

What should you rinse a volumetric flask with?

Answer 35

Water. Rinsing with the solution being measured out would increase the amount of that solution in the volumetric flask by an unknown quantity.

Question 36

What should you rinse a conical flask with?

Answer 36

Water. Rinsing with the analyte would increase the amount of analyte present in the conical flask by an unknown quantity.