Light does not travel at a constant speed in a vacuum, compared to in air, because the light is being absorbed by atoms and molecules in the air. But light does travel at a constant speed in a vacuum.
So I agree with A
All that talk about moving forward is irrelevant (I think)
Answer:
401.17 K is the minimum temperature at which the reaction will become spontaneous under standard state conditions.
Explanation:
The expression for the standard change in free energy is:
Where,
is the change in the Gibbs free energy.
T is the absolute temperature. (T in kelvins)
is the enthalpy change of the reaction.
is the change in entropy.
Given at:-
Temperature = 25.0 °C
The conversion of T( °C) to T(K) is shown below:
T(K) = T( °C) + 273.15
So,
T₁ = (25.0 + 273.15) K = 298.15 K
= 128.9 kJ/mol
= 33.1 kJ/mol
Applying in the above equation, we get as:-

= 0.32131 kJ/Kmol
So, For reaction to be spontaneous, 
Thus, For minimum temperature:-

<u>Hence, 401.17 K is the minimum temperature at which the reaction will become spontaneous under standard state conditions.</u>
Answer:
a. decrease the amount of the common ion in the system
Explanation:
The correct option is - a. decrease the amount of the common ion in the system
Reason -
Adding a common ion decreases solubility, as the reaction shifts toward the left to relieve the stress of the excess product.
Adding a common ion to a dissociation reaction causes the equilibrium to shift left, toward the reactants, causing precipitation.
Answer:
a. Sn or Si ⇒ Sn
b. Br or Ga ⇒ Ga
c. Sn or Bi ⇒ similar in size
d. Se or Sn ⇒ Sn
Explanation:
The larger atom has a larger atomic radius. We have to consider how varies the atomic radius for chemical elements in the Periodic Table. In a group (column), the atomic radius increases from top to bottom while in a period (file), it increases from right to left.
a. Sn or Si ⇒ Sn
They are in the <u>same group</u>. Sn is on the top, so it has a larger atomic radius.
b. Br or Ga ⇒ Ga
They are in the <u>same period</u>. Ga is located at the left so it has a larger atomic radius.
c. Sn or Bi ⇒ similar
They are not in the same group neither the same period. Bi is located more at the bottom, so it would be larger than Sn, but Bi is also at the right side, so it would be smaller than Bi. Thus, they have comparable sizes.
d. Se or Sn⇒ Sn
They are not in the same group neither the same period. Se is located at the top and right side compared to Sn, so Sn is the larger atom.