Yes, free electrons appear in balanced redox reaction equations. However, this is only true for half-reactions. This is because redox reactions primarily involve the transfer of electrons, which are better visualized if explicitly shown in the balanced reactions. In reduction reactions, electrons are placed on the left side of the equation. Oxidation reactions show electrons on the right side of the equation.
Explanation:
A half reaction is either the chemical reaction or reduction reaction part of an oxidoreduction reaction. A half reaction is obtained by considering the amendment in chemical reaction states of individual substances concerned within the oxidoreduction reaction. Half-reactions are usually used as a way of leveling oxidoreduction reactions.The half-reaction on the anode, wherever chemical reaction happens, is Zn(s) = Zn2+ (aq) + (2e-).
The metal loses 2 electrons to create Zn2+. The half-reaction on the cathode wherever reduction happens is Cu2+ (aq) + 2e- = Cu(s).
Here, the copper ions gain electrons and become solid copper.
The total number of atoms make up the products :
D) 1 carbon, 4 hydrogen, and 4 oxygen
<h3>Further explanation
</h3>
Complete combustion of Hydrocarbons with Oxygen will produce CO₂ and H₂O compounds.
If O₂ is insufficient there will be incomplete combustion produced by CO and H and O
Hydrocarbon combustion reactions (especially alkanes)
For combustion of methane (CH₄) and two molecules of oxygen (O₂).

The number of atoms make up the products
CO₂ : 1 carbon, 2 oxygen
2H₂O : 4 hydrogen , 2 oxygen
Answer:
No of neutrons and protons decides mass of the atom. Electrons having negligible
mass are ignored.
Mass of atom
Mass of atom= sum of no of protons(Z) and neutons(N)
=Z+N
For eg:
In hydrogen atom,
Mass of H= Z+N
=1+0
=1 AMU
<u>Given:</u>
Mass of the ball = 35.2 kg
Momentum = 218 kg m/s
<u>To determine:</u>
The velocity of the ball
<u>Explanation:</u>
Momentum (p) of an object is the product of its mass (m) and velocity (v)
p = m*v
v = p/m = 218 kg.ms-1/35.2 kg = 6.19 m/s
Ans: The velocity of the ball is 6.19 m/s
answer A.a new substance is formed