Answer:
The answer to your question is: letter A
Explanation:
a) A + B ⇒ AB + heat It is an exothermic reaction because heat is released.
b) A + BΔ ⇒ AB It heat added to the reactants , then it is an endothermic reaction.
c) heat + BC ⇒ B + C It's an endothermic reaction because heat is added to the reactants.
d) B + heat + CD ⇒ BD + C It's and endothermic reaction because heat is added to the reactants.
Answer
A. molecules
Explanation
When atoms or elements combine, they are called molecules. When molecules combine they form compounds.
Answer:

Explanation:
Hello!
In this case, since the undergoing chemical reaction is:

We first need to identify the limiting reactant given the masses of nitrogen and hydrogen:

It means that only 0.647 moles of ammonia are yielded, so the resulting enthalpy change is:

Best regards!
Answer:
Potassium
Explanation:
It's in group 1 in the periodic table of elements