How does changing the concentration of Zn2+(aq) ions (0.2, 0.4, 0.6, 0.8, 1.0) (moldm-3) affect the voltage (V) of the voltaic cell consisting of Zinc and Copper half cells? Aim
To see the relationship between increasing the concentration of Zinc ions and the voltage that is obtained from voltaic cell. The concentration of zinc ions can be directly manipulated by changing the concentration of a zinc sulphate aqueous solution, and the voltage will be measured using an electronic voltmeter. Background Information
A voltaic cell produces electrical energy as a result of a spontaneous redox process. The electron transfer characteristic of such a process is made to occur in two separate half-cells. Electrons released during an oxidation half-equation must flow through a wire or other external circuit before they can be accepted in a reduction half-equation. Consequently an electrical current is made to flow (Chem Ed)
Two half equations could be written based on the voltaic cell that was shown as Figure 1. These two half equations are stated below:- Zn(S)→Zn2+(aq)+2e-
Furthermore, by combing these two half equation a final equation could be written. This final equation is shown below:- ZnS+Cu2+(aq)→Zn2++Cu(s)
If the concentration of Zn2+(aq) ions increases, the current of the voltaic cell also increases which this means the voltage also increases. This is because by increasing the concentration of Zn2+(aq), the number of ions increases as well thus more available ions result in higher chance of occurrence of oxidation or reduction reaction.
Identify: Changing the concentration of Zn2+(aq) ions (0.2, 0.4, 0.6, 0.8 1.0) (moldm-3) Reason and method of manipulation: In order to have reliable results from this lab 5 trials and 5 different concentrations were used. This increases the validity of the results that are going to be obtained from this lab. The concentration of Zn2+(aq) ions is manipulated by using 5 different concentrations of ZnSO4(aq).Since this is an ionic compound, it will dissolve in water; i.e. 1 mol of ZnSO4 will produce 1 mol of Zn2+ ions. Thus these 5 concentrations were used (0.2, 0.4, 0.6, 0.8 1.0) moldm-3. Only the concentration of Zn2+(aq) is going to be manipulated because only one variable is being tested. NO MAN the concentration of SO4 ions will change also but just say that we don’t take it into account and that it does not affect the experiment… Dependent Variable
Identify: The voltage of the voltaic cell (V)
Reason & method of calculation: The electronic voltmeter is connected in parallel circuit to Zinc strip and Copper Zinc (what’s copper zinc) Say connected to the zinc and copper electrodes. The voltmeter reads the current and shows the voltage. I’d remove this bit, looks a bit confusing because you’re mentioning current now.. Or make it sound clearer Next the voltage from all the 5 trials and 5 concentrations are going to be noted down. After that the average of the voltages will be calculated using the Mean formula which is shown below:- X=i=1nXin
Next the standard deviation is going to be calculated in order to see how far are the numbers are from the mean. The formula for standard deviation is mentioned below:- ∑(X-X)2(n-1)
X= Each score
X= The mean of the score
n = Number of values
∑= Sum across the values
Table 1: Controlled Variable
| Why it is going to be controlled?
| How it is going to be controlled?
| Temperature of solutions of Zinc sulphate and Copper sulphate
| Increasing the temperature decreases the voltage. That is because the current cannot reach equilibrium in higher temperature, therefore by decreasing the voltage the system maintains the equilibrium (Nihil Nonscio) Thus both solutions should have the same temperature in order to have a fair experiment.
| The solutions will be requested to have the standard temperature which is 273 K...
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