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.
The net force = -5 N
The direction : to the left(negative sign)
<h3>Further explanation
</h3>
Net force : the sum of all forces acting on an object
Force is a vector quantity that has both magnitude and direction,
We agree that the move up and to the right is a positive sign, while down and to the left is a negative sign.
The direction of the force (horizontal motion) is to the right (+32 N), and to the left (-37 N), so the net force :

Answer&Explanation:
The unit used to measure Heat is joule equal to that of Energy and is abbreviated as (J)
Answer:
half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive ...
Explanation:
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