What type of reaction is shown in this thermochemical equation? a + b + heat → c + d
endothermic
combination
decomposition
exothermic

Option (a) is the correct answer.

Explanation:

A chemical reaction in which there will be absorption of heat energy by the reactant molecules is known as endothermic reaction.

For example, is an endothermic reaction.

On the other hand, a chemical reaction in which there will be release of heat energy is known as an exothermic reaction.

For example, is an exothermic reaction.

Therefore, we can conclude that the given thermochemical equation shows endothermic type of reaction.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.