Answer:
Only 
gives spontaneous reaction.
Explanation:
A redox reaction will be spontaneous if standard reduction potential (
) of the reaction is positive. Because it leads to negative standard gibbs free energy change (
), which is a thermodynamic condition for spontaneity of a reaction.
Where 
and 
represents standard reduction potential of reduction half cell and standard reduction potential of oxidation half cell.
(1) Oxidation: 
; 
Reduction: 
; 
So, 
Hence this pair will give spontaneous reaction.
(2) Similarly as above, 
Hence this pair will give non-spontaneous reaction.
(3) Similarly as above, 
Hence this pair will give non-spontaneous reaction.
(4) Similarly as above, 
Hence this pair will give non-spontaneous reaction.
Answer:
230hz
Explanation:
Hello,
To solve this question, we gave to use the relationship between velocity-frequency-wavelength to find the frequency in this question.
V = Fλ
V = velocity or speed of the wave
F = frequency of the wave
λ = wavelength of the wave
Data;
V = 414m/s
λ = 1.8m
f = ?
V = fλ
f = v/λ
f = 414/1.8
f = 230hz
The frequency of the wave is 230hz
