Explanation:
Physical changes only change the appearance of a substance, not its chemical composition.
Chemical changes cause a substance to change into an entirely substance with a new chemical formula.
Chemical changes are also known as chemical reactions. The “ingredients” of a reaction are called reactants, and the end results are called products
<u>Answer:</u> The chemical equation is written below.
<u>Explanation:</u>
Every balanced chemical equation follows law of conservation of mass.
This law states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form. This also means that total number of individual atoms on reactant side must be equal to the total number of individual atoms on the product side.
The chemical equation for the reaction of elemental boron and oxygen gas follows:

By Stoichiometry of the reaction:
4 moles of elemental boron reacts with 3 moles of oxygen gas to produce 2 moles of diboron trioxide.
The chemical equation for the reaction of diboron trioxide and water follows:

By Stoichiometry of the reaction:
1 mole of diboron trixoide reacts with 3 moles of water to produce 2 moles of boric acid.
Hence, the chemical equations are written above.
Answer:
12.33 cal/sec
Explanation:
As we know,
1 Kcal = 1000 cal
So,
0.74 Kcal = X cal
Solving for X,
X = (0.74 Kcal × 1000 cal) ÷ 1 Kcal
X = 740 cal
Also we know that,
1 Minute = 60 Seconds
Therefore, in order to derive cal/sec unit replace 0.74 Kcal by 740 cal and 1 min by 60 sec in given unit as,
= 740 cal / 60 sec
= 12.33 cal/sec