Aim: To investigate the effect of varying voltage on the rate of an electrolysis reaction of copper (I) chloride.
Hypothesis: as voltage increases, the rate of redox reaction/change in mass of copper will increase
Accuracy:**** How close your experimentally derived number is to the “true” or “real” quantity being measured. This relies on scale.
Precision: How close the repeat values or a given trial are to each other, OR the fineness of the scale on the instrument being used to take measurements
Reliability: If we conduct more trials and find that the results we get each time are not significantly different from the others
Validity: No other variables, known or unknown, are impacting the independent or dependent variables (fair tests)
Uncertainty/Error
Measurement uncertainty: uncertainty which is a property of the measuring instrument
- Unavoidable, quantifiable, hopefully very small
Systematic Error: Impacts each trial in the same direction away from the true value
- Bias in direction
Random Error: Impacts each trial but with no bias in direction, and if truly random, should cancel out with respect to accuracy
Errors for experiment
Random:
- Measurement error
- Measuring mass
- Human error (timing 30 seconds)
Systematic
- At a certain voltage, water will undergo redox and thus rate of redox reaction of CuCl2 decreases
- As voltage increases, temperature will increase, and thus SRP values will change
- If tap water is used, ions in tap water could potentially undergo redox and decrease rate of redox reaction of CuCl2
- Concentration of solution is 2 mol/L, thus SRP values do not apply
Hazards:
- Chlorine gas is produced at high voltages
- Copper Chloride is used
Risks:
- Chlorine gas is toxic
- Copper chloride is irritative
- Inhalation results in irritation of lungs
- Consumption results in irritation of stomach
- May damage kidneys
Minimise risks:
- Carry out experiment in a fumehood
- Carry out experiment in well ventilated area
- Provide guidelines/safety instructions, or hazard/warning information on signs
- Wash hands immediately after exposure to CuCl and after the experiment
- Wear safety goggles, lab coat and gloves
Improve experiment
- Carry out more trials
- Use cucl at 1 mol/L so SRP values apply
Hazard
- Potential event that causes harm
- Also an object that causes harm
- E.g., dangerous substances
Risk
- Occurrence of event that causes harm
- Also the likelihood of an event that causes harm
- E.g., effect of dangerous substances
Minimise Risk
- Things that prevent the occurrence of events that cause harm
- E.g., wear protective equipment
- If gas is produced, carry out experiment in well ventilated area
- prevent the risk or reduce the loss of control of the hazard
- reduce the effects