Question

1. Which of the following chemical reactions is an oxidation-reduction reaction?
Answer
WO3 + 3H2 W + 3H2O
KNO3 + LiCl LiNO3 + KCl
CaSO4 + 2NaCl Na2SO4 + CaCl2
Mg(NO3)2 + 2HBr MgBr2 + 2HNO3

2. According to the collision theory and model created to explain the collision theory, what is the best explanation for why a higher concentration makes a reaction go faster?
There are more collisions per minute.
It increases the distance between the particles.
It increases the average kinetic energy of the particles.
It increases the average kinetic energy and there are more collision per minute

Answer 1

1) Answer is: WO3 + 3H2 → W + 3H2O.

Reduction reaction: W⁺⁶ + 6e⁻ → W⁰.

Oxidation reaction: H₂ → 2H⁺¹ + 2e⁻ / ×3; 3H₂ → 6H⁺¹ + 6e⁻.

Wolfram change oxidation number from +6 to 0 (reduction) and hydrogen change oxidation number from 0 to 01 (oxidation).

In other examples, elements do not change their oxidation numbers.

2) Answer is: It increases the average kinetic energy and there are more collision per minute.

The collision theory states that a certain fraction of the collisions (successful collisions) cause significant chemical change.

The successful collisions must have enough energy (activation energy).

Chemical bonds are broken and new bonds are formed.

Particles are in constant, random motion and possess kinetic energy, molecules faster and have more collisions.

Answer 2

Explanation:

1.  When there is loss of electrons or increase in oxidation state of an element in a chemical reaction then it is known as oxidation.

Whereas when there is gain of electrons or decrease in oxidation state of an element in a chemical reaction then it is known as reduction.

For example, $WO_{3} + 3H_{2} \rightarrow W + 3H_{2}O$

Oxidation half-reaction: $3H_{2} \rightarrow 3H_{2}O + 6e^{-1}$

Reduction half-reaction: $W^{+6} + 6e^{-1} \rightarrow W$

Therefore, out of the given options $WO_{3} + 3H_{2} \rightarrow W + 3H_{2}O$ chemical reaction is an oxidation-reduction reaction.

Whereas in other given reactions, there is no change in oxidation state of atoms. Hence, they are not oxidation-reduction reactions.

2.   According to collision theory, more is the number of collisions occurring in a chemical reaction more faster will be the rate of reaction.

Therefore, higher is the concentration that is, more will be the number of reactants present in the chemical reaction. Therefore, more will be the number of collisions.

Hence, we can conclude that there are more collisions per minute.