Answer:
ΔGº = --29 kJ
Explanation:
The equation to use is ΔGº = -nFEºcell
where n is the number of mole of electrons exchanged in the redox equation
F is Faraday´s constant 96485 C/mole
Eº cell potential
Ni²⁺(aq) + 2e⁻ ⇒ Ni (s) Eºred = -0.25 V
Cd(s) ⇒ Cd²⁺ + 2e⁻ Eºox = +0.40 V
Eºcell = 0.40 V -0.25 V = 0.15 V
ΔGº = - 2 mole x 96485 C/mol x 0.15 V = -2.9 x 10⁴J = -29 kJ
(remember 1 Coulomb x 1 Volt = 1 Joule)
PV = nRT, or (pressure)(volume) = (amount of gas)(universal gas constant)(temperature)
<span>You're solving for pressure, so start by rearranging the equation: </span>
<span>p = (nRT)/V </span>
<span>You're given temperature; all you need to do is convert it to Kelvin. (The universal gas constant is 8.31 J/(Kmol), so the units for temperature need to be the same.) </span>
<span>But how to figure out the rest? The question doesn't give you the size of the flask or number of moles, but it does tell you that these things don't change throughout the problem. Because they're constant, we don't have to know exactly what they are - we just have to know the *combined values* of the constants. (If this is confusing, think about it this way: a small amount of gas in a small flask will exert the same amount of pressure as a large amount of gas in a large flask, as long as the ratios are kept equal - it doesn't matter if it's 2 moles in 2 L, or 1 mole in 1 L.) </span>
<span>To figure out this constant, go back to the opening, where you're given temperature and pressure. </span>
<span>pV = nRT </span>
<span>Remember to convert celsius to kelvin! </span>
<span>(254mm Hg)(V) = nR(330K) </span>
