Answer: 
Explanation: A double displacement reaction is one in which exchange of ions take place.
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

Answer:
1. active site
2. substrate.
3. activity
4. cofactor
5. complex
6. coenzyme.
Explanation:
1. A substrate binds to an enzyme at the active site where the reaction occurs.
2. In a catalyzed reaction, a reactant is often called a substrate.
3 activity is a measure of how fast an enzyme can convert the reagent to the product.
4. An inorganic substance necessary for the function of some enzymes is called a cofactor.
5. When properly aligned, the enzyme and substrate form an enzyme-substrate (ES) complex.
6. A small organic molecule necessary for the function of some enzymes is called a coenzyme.
P1/V1=P2/V2
1/22.4=4/x
X=4 multiple by 22.4
V2=89.6L
Answer:
covalent bonds
Explanation:
Nitrogen atoms will form three covalent bonds (also called triple covalent) between two atoms of nitrogen because each nitrogen atom needs three electrons to fill its outermost shell.
(if it is still confusing i have another way of explaining so jus let me know :)
Answer: Nuclei combine to form a heavier nucleus, releasing energy.
Explanation: e.g two deuterium nucleus (Hydrogen-2 isotopes) forms an He nucleus and energy is released.