4.1 Intro for Reactions and 4.2 Net Ionic Equations

Multiple Choice

Another student is asked to formulate a hypothesis about what would happen to sodium metal when it is placed in water. Which of the following hypotheses indicates that the student thinks a chemical change will occur?

• If sodium is added to water, it will dissolve

• If sodium is added to water, heat and light will be released

• If sodium is added to water, the total mass will be the same

• If sodium is added to water, the water will remain a clear, colorless liquid

Open Ended

A student is carrying out various experiments in a laboratory. In one experiment, the student mixes two clear, colorless solutions together and a yellow precipitate is formed. The student determines that this is evidence of a chemical reaction? Do you agree? Justify your answer.

Multiple Choice

A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place?

• The resulting solution is colorless.

• The temperature of the reaction mixture increases.

• The total volume of the mixture is approximately equal to the sum of the initial volumes.

• The resulting solution conducts electricity.

Multiple Choice

A student was asked to formulate a hypothesis about what would happen if 100.mL of 0.1M NaOH(aq) at 25°C was combined with 100.mL of 0.1M MgCl2(aq) at 25°C. Which of the following hypotheses indicates that the student thought a chemical change would occur?

• The volume of the resulting solution will be equal to the sum of the volumes of the original solutions.

• The mass of the resulting solution will be equal to the sum of the masses of the original solutions.

• The resulting solution would contain a precipitate.

• The resulting solution will be clear.

Multiple Choice

A student was studying physical and chemical changes. The student carried out some procedures in the laboratory and recorded observations. For one of the procedures, the student concluded that a physical change took place, but not a chemical change. Which of the following could have been the results of the procedure?

• A cube of metal was changed into a flat sheet of metal.

• When two liquids at room temperature were combined in a beaker, the beaker became hot.

• When two clear liquids were combined, the resulting mixture was cloudy.

• When a colorless liquid was added to a blue liquid, the resulting solution was yellow.

Multiple Choice

Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid?

• NaF(aq) + HCl(aq) → NaCl(aq) + HF(aq)

• Na⁺(aq) + F^-(aq) + H⁺(aq) + Cl^-(aq) → Na⁺(aq) + Cl^-(aq) + HF (aq)

• Na⁺ (aq) + Cl^- (aq) → NaCl (aq)

• F^-(aq) + H⁺(aq) → HF(a)

Multiple Choice

Equal volumes of 0.2M solutions of lead(II) nitrate and potassium bromide are combined to form lead(II) bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?

• Pb²⁺ (aq) + 2Br^- (aq) → PbBr₂ (s)

• K⁺(aq) + NO₃^- (aq) → KNO₃ (aq)

• Pb²⁺(aq) + 2NO₃^- (aq) + 2K⁺ (aq) + 2Br^- (aq) → 2K⁺(aq) + 2NO₃^-(aq) + PbBr₂(s)

• Pb(NO3)₂ (aq) + 2KBr(aq) → PbBr₂ (s) + 2KNO₃ (aq)

Multiple Choice

The reaction between aqueous strontium chloride (SrCl₂) and aqueous potassium sulfate (K₂SO₄) forms a precipitate of strontium sulfate (SrSO₄). Which of the following represents the net ionic equation for the reaction?

• Cl^-(aq) + K⁺(aq) → KCl (aq)

• Sr²⁺ (aq) + SO₄^2- (aq) → SrSO₄ (s)

• Sr²⁺ (aq) + 2Cl^- (aq) + SO₄^2- (aq) + 2K⁺ (aq) → SrSO₄ (s) + 2Cl^- (aq) + 2K⁺ (aq)

• SrCl₂ (aq) + K₂SO₄ (aq) → SrSO₄ (s) + 2KCl (aq)

Multiple Choice

Equal volumes of 0.2 M solutions of lead (II) Nitrate and potassium bromide are combined to form lead (II) bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?

• Pb²⁺ (aq) + 2Br^- (aq) --> PbBr₂ (s)

• K⁺ (aq) + NO₃^- (aq) --> KNO₃ (aq)

• Pb²⁺ (aq) + 2NO₃^- (aq) + 2K⁺ (aq) +2 Br^- (aq) --> 2K⁺ (aq) + 2NO₃^- (aq) + PbBr₂ (s)

• Pb(NO₃)₂ (aq) + 2KBr (aq) --> PbBr₂ (s) + 2KNO₃ (aq)