(1) Islands are always surrounded by bodies of water, in this case oceans. These islands tend to have more 'stable climates' and 'smaller temperature fluctuations' due to the specific heat of water, which is quite high, 4180 J/kg C. The higher the specific heat, the more the energy needed to raise the temperature of the substance. Land requires less energy to raise it's temperature than water due to it's lower specific heat. Thus, islands tend to have more stable temperatures than regions surrounded by land.
(2) Based on the conditions provided, the thermochemical equation for the reaction should be:
2NaHCO₃ (s) ---> Na₂CO₃ (s) + H₂O (g) + O₂ (g)
This is a decomposition reaction, as it explains that the baking soda breaks down into the products. All we had left to do is balance the equation, adding 2 as the coefficient of the reactant.
(3) Let's rewrite the given equations:
First chemical reaction: H₂(g) + F₂(g) ---> 2HF(g), ΔH₁ = –537 kJ.
Second chemical reaction: C(s) + 2F₂(g) ---> CF₄(g), ΔH₂ = –680 kJ
Third chemical reaction: 2C(s) + 2H₂(g) ---> C₂H₄(g), ΔH₃ = +52.3 kJ.
Fourth chemical reaction: C₂H₄(g) + 6F₂(g) ---> 2CF₄(g) + 4HF(g), ΔH₄ = ?
Now the 'fourth chemical reaction' is the one in which we need to determine the enthalpy:
ΔH₄ = 2(ΔH₁) + 2(ΔH₂) - ΔH₃,
ΔH₄ = 2(–537) + 2(–680) - 52.3 = -2486.3 kJ
