Answer :
(a) displacement reaction
(b) combination reaction
(c) disproportionation reaction
(d) displacement reaction
Explanation :
(a) The given balanced chemical reaction is,

This reaction is a single replacement reaction or displacement in which the the more reactive element (Fe) replace the less reactive element (H).
(b) The given balanced chemical reaction is,

This reaction is a combination reaction in which the two reactants molecule combine to form a large molecule or single product.
(c) The given balanced chemical reaction is,

This reaction is a disproportionation reaction in which the chemical species gets oxidized and reduced simultaneously. It is also considered as a redox reaction.
(d) The given balanced chemical reaction is,

This reaction is a single replacement reaction or displacement in which the the more reactive element (Ag) replace the less reactive element (Pt).
Answer:
Ea=5.5 Kcal/mole
Explanation:
Let rate constant are
and
at temperature
and 
By using Arrhenius equation at two different two different temperature,
By putting value of R=2 cal/mole.K

By rounding off upto 2 significant figure;

Answer:
alpha decay, because alpha particles have two protons and two neutrons. If the isotope has an atomic number two less than the original, it lost two protons, the same amount as in an alpha particle.
Explanation:
I can’t answer the exact thing, but I know how to do it. One of the nitrogen bases always pairs with a different one, so once you know what pairs with what you just write it down. If you need more help just ask :) tip: one base will only join with a different one. One won’t join to multiple (from what I know as of now)
Explanation: Oxygen plays a very vital role in the life of aquatic animals. The dissolved oxygen in the water helps them to breathe under water.
Optimum level of oxygen for deep living animals like oysters, bottom feeders, crabs is around (1-6 mg/L), while the animals living on the upper side like fishes require a higher amount of around (4-6 mg/L).
If the oxygen concentration in the pond is not optimum, there will no aquatic life and hence, the ecosystem will be affected.
Hence, oxygen concentration affects the fishes that live in the pond to a higher extent.