State the energy conversion that takes place in this cell - NSC Physical Sciences - Question 8 - 2021 - Paper 2

To find the mass, we first calculate the number of moles of AgNO3 needed:

Given:

• Volume = 150 cm³ = 0.150 dm³
• Concentration = 1 mol/dm³ (assumed standard concentration)

Using the formula:

$n = c imes V$

we have:

$n = 1 ext{ mol/dm}^3 imes 0.150 ext{ dm}^3 = 0.150 ext{ mol}$

Now, we calculate the mass using the molar mass of AgNO3:

• Molar Mass of AgNO3 = 170 g/mol

$m = n imes M$

Thus:

$m = 0.150 ext{ mol} imes 170 ext{ g/mol} = 25.50 ext{ g}$

A reducing agent is a substance that loses electrons during a chemical reaction, thereby causing the reduction of another substance. It donates electrons and becomes oxidized in the process.

Copper (Cu) is the reducing agent in this cell as it loses electrons.

The balanced equation for the reaction that takes place in the electrochemical cell is:

$Cu(s) + 2Ag^+(aq) \rightarrow Cu^{2+}(aq) + 2Ag(s)$

The initial emf (E°) of the cell can be calculated using standard reduction potentials. Given:

• The standard reduction potential for the half-reaction of Cu is approximately +0.34 V, and for Ag is approximately +0.80 V.

The emf can be calculated using the formula:

$E_{cell} = E_{cathode} - E_{anode}$

Substituting values:

$E_{cell} = 0.80 V - 0.34 V = 0.46 V$

The emf of the cell will DECREASE if the concentration of the copper ions in half-cell A increases. This is based on Le Chatelier's principle, where increasing the concentration of a reactant shifts the equilibrium, potentially affecting cell voltage.