AP Chem Unit 4.7: Types of Chemical Reactions

2 H2O2(aq) → 2 H2O(l) + O2(g) ΔH° = −196 kJ/molrxn The decomposition of H2O2(aq) is represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H2O2(aq) at a constant temperature of 300. K and recorded the concentration of H2O2 as a function of time. The results are given in the table below. Which of the following identifies the element(s) being oxidized and reduced in the reaction?

Oxygen is both oxidized and reduced.

2 MnO4-(aq) + 10 Br-(aq) + 16 H+(aq) → 2 Mn2+(aq) + 5 Br2(aq) + 8 H2O(l) How many electrons are transferred in the reaction represented by the balanced equation above?

10

The following questions refer to the reactions represented below. (A) H2SeO4(aq) + 2 Cl-(aq) + 2 H+(aq) → H2SeO3(aq) + Cl2(g) + H2O(l) (B) S8(s) + 8 O2(g) → 8 SO2(g) (C) 3 Br2(aq) + 6 OH-(aq) → 5 Br-(aq) + BrO3-(aq) + 3 H2O(l) (D) Ca2+(aq) + SO42-(aq) → CaSO4(s) (E) PtCl4(s) + 2 Cl-(aq) → PtCl62-(aq) A reaction in which the same reactant undergoes both oxidation and reduction

3 Br2(aq) + 6 OH-(aq) →5 Br-(aq) + BrO3-(aq) + 3 H2O(l)

Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set. Refer to the following types of chemical or physical changes. (A) Oxidation-reduction reaction (B) Brønsted-Lowry acid-base reaction (C) Sublimation (D) Dehydration (E) Precipitation Occurs when aqueous solutions of ammonia and vinegar are mixed

Brønsted-Lowry acid-base reaction

The diagrams above represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred?

D; free- floating Na+ and NO3- ions, clumped Ag+ and Cl- ions

When C2H4(g) reacts with H2(g), the compound C2H6(g) is produced, as represented by the equation above. The reaction is correctly classified as which of the following types?

Oxidation-reduction, because H2(g)H2(g) is oxidized.

I2(aq)+C6H8O6(aq)→C6H6O6(aq)+2I−(aq)+2H+(aq) The compound C6H8O6 reacts with I2 according to the reaction represented by the equation above. The reaction is correctly classified as which of the following types?

Oxidation-reduction, because I2I2 is reduced.

5 H2O2(aq) + 2 MnO4-(aq) + 6 H+(aq) → 2 Mn2+(aq) + 8 H2O(l) + 5 O2(g) In a titration experiment, H2O2(aq) reacts with aqueous MnO4-(aq) as represented by the equation above. The dark purple KMnO4 solution is added from a buret to a colorless, acidified solution of H2O2(aq) in an Erlenmeyer flask. (Note: At the end point of the titration, the solution is a pale pink color.) Which element is being oxidized during the titration, and what is the element's change in oxidation number?

Oxygen, which changes from -1 to 0

A precipitation reaction

Pb2+(aq) + CrO42-(aq) → PbCrO4(s)

H2Se(g) + 4 O2F2(g) → SeF6(g) + 2 HF(g) + 4 O2(g) Which of the following is true regarding the reaction represented above?

The oxidation number of Se changes from -2 to +6.