Three electrolytic cells containing solutions of CuNO3, Sn(NO3)2, and Fe(NO3)3, respectively, are connected in series. A current of 2.2 A is passed through the cells until 3.10 g of copper has been deposited in the cell.
(a) What masses of tin and iron are deposited?
tin
g
iron
g
(b) For how long did the current flow?
do i just use It=nF?? not sure how to do it with 3 diff substances tho..
135 c
To determine the masses of tin and iron deposited, as well as the duration of current flow, we need to use the concept of Faraday's law of electrolysis. This law states that the amount of substance deposited or liberated at an electrode is directly proportional to the quantity of electricity passed through the electrolyte.
(a) To calculate the masses of tin and iron deposited, we need to determine the moles of copper deposited first, as it serves as a reference for the other two elements. Given that 3.10 g of copper has been deposited and the molar mass of copper is approximately 63.55 g/mol, we can use the following equation to calculate the moles of copper deposited:
moles of copper = mass of copper / molar mass of copper
= 3.10 g / 63.55 g/mol
Next, we need to determine the ratio of moles deposited among the three substances, which can be obtained from the balanced chemical equation for their respective reduction reactions:
Cu²⁺(aq) + 2e⁻ → Cu(s)
Sn²⁺(aq) + 2e⁻ → Sn(s)
Fe³⁺(aq) + 3e⁻ → Fe(s)
From the balanced equation, we can see that for every 2 moles of electrons transferred, 1 mole of copper, tin, or iron is deposited. Therefore, the ratio of moles of copper deposited to moles of tin and iron deposited is 1:1:1.
Since we have calculated the moles of copper deposited, the moles of tin and iron deposited will be the same:
moles of tin deposited = moles of iron deposited = moles of copper deposited
To find the masses of tin and iron, we can use their respective molar masses:
mass of tin = moles of tin deposited * molar mass of tin
mass of iron = moles of iron deposited * molar mass of iron
You can find the molar masses of tin and iron from the periodic table.
(b) To calculate the duration of current flow, we need to use Faraday's law. The equation you mentioned, It = nF, is correct. However, since we have three different substances, we need to consider their individual Faraday's constant.
The equation can be modified as follows:
It = (n₁F₁ + n₂F₂ + n₃F₃)
Where:
n₁, n₂, and n₃ are the moles of copper, tin, and iron respectively,
F₁, F₂, and F₃ are the Faraday's constants for copper, tin, and iron respectively.
Faraday's constant (F) is a constant representing the charge of one mole of electrons, which is approximately 96,485 C/mol.
To find the Faraday's constants for each substance, we need to know the number of electrons involved in their respective reduction reactions. For copper, it is 2 electrons, for tin, it is 2 electrons, and for iron, it is 3 electrons. Therefore:
F₁ = 2 * F
F₂ = 2 * F
F₃ = 3 * F
By substituting n₁, n₂, n₃, F₁, F₂, F₃, and the total current (I = 2.2 A) into the equation, we can solve for time (t):
It = (n₁F₁ + n₂F₂ + n₃F₃)
2.2 A * t = (n₁ * 2F + n₂ * 2F + n₃ * 3F)
Simplifying the equation will give you the value for the flow duration, t.
Note: Make sure to use consistent units for all the calculations.