1. Hydrogen and nitrogen combine to form ammonia. When nitrogen and hydrogen bond, nitrogen pulls the electrons from hydrogen toward itself. Which statement about the reactants is correct?
A) Hydrogen is oxidized, and nitrogen loses electrons.
B) Hydrogen is oxidized, and nitrogen is reduced.
C) Hydrogen gains electrons, and nitrogen is reduced.
D) Hydrogen is reduced, and nitrogen is oxidized.

2. Which phrase best defines a redox reaction?

A) A reaction in which the number of oxygen atoms is reduced.
B) A reaction in which elements are transferred between different atoms.
C) A reaction is which oxygen combines with different atoms.
D) a reaction in which elements are released from the system.

3.Which statement describes the process of oxidation?

A) Oxidation results in a loss of electrons, so the oxidation number increases.
B) Oxidation results in a gain of electrons, so the oxidation number increases.
C) Oxidation results in a gain of electrons, so the oxidation number decreases.
D) Oxidation results in a loss of electrons, so the oxidation number decreases.

4. Which chemical equation represents a redox reaction?
A) TiCl4(s) + 2H2O(g) → TiO2(s) +4HCl(g)
B) CaO(s) + SiO2(s) → CaSiO3(l)
C) CaCO3(s) → CaO(s) + CO2(g)
D)Fe2O3(s) + 2Al(s) → Al2O3(s) +2Fe(l)

5. Which elements are oxidized and reduced in the reaction below?
Br2 (l) + 2NaI(aq) → I2 (s) + 2NaBr(aq)

A) Bromine (Br) is oxidized, and iodine (I) is reduced.
B) Iodine (I) is oxidized, and bromine (Br) is reduced.
C) Sodium (Na) is oxidized, and bromine (Br) is reduced.
D) Bromine (Br) is oxidized, and sodium (Na) is reduced.