Answer:
Reaction A, B, E and F are exothermic reactions.
Explanation:
Exothermic reactions are defined as the reactions in which energy of reactants is more than the energy of the products. In these reactions, energy is released by the system.
The total enthalpy of the reaction 
comes out to be negative.
Endothermic reactions are defined as the reactions in which energy of products is more than the energy of the reactants. In these reactions, energy is absorbed by the system.
The total enthalpy of the reaction comes out to be positive.
So, from the given option reaction which are exothermic are with negative value that enthalpy of reaction and those are:
1) 
,ΔH = -1203 kJ/mol
2)
,ΔH =-176 kJ/mol
3) 
,ΔH = -393.5 kJ/mol
4) 
,ΔH =-891 kJ/mol
Answer:
Convection.
Explanation:
Let us define each of the type of thermal transfer first:
- radiation is heat transfer that does not include contact between the objects. It's mediated by infra-red radiation, waves from the invisible radiation spectrum.
- conduction is heat transfer which is mediated through direct contact between objects (holding a hot cup of tea, for example)
- convection is a heat transfer found in gases and liquids. Due to different temperatures in two parts of liquid, there will also be a different density ( hotter parts have lower density). Lower density parts will start moving upwards while higher density parts, due to gravity, will move downward. As they move, they will gain or receive heat, which will cause new temperature differences and the moving will restart.
2nd family
calcium is in the second family
