Unit 4

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 precipitate reaction occurred?

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A 2 mol sample of F₂(g) reacts with excess NaOH(aq) according to the equation above. If the reaction is repeated with excess NaOH(aq) but with 1 mol of F₂(g), which of the following is correct?

• The amount of OF₂(g) produced is doubled.

• The amount of OF₂(g) produced is halved.

• The amount of NaF(aq) produced remains the same.

• The amount of NaF(aq) produced is doubled.

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-7

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) + 2 Br⁻ (aq) → PbBr₂ (s)

• K⁺ (aq) + NO₃⁻ (aq) → KNO₃ (aq)

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

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

Tags

NGSS.HS-PS1-7

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.

Tags

NGSS.MS-PS1-2

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.

Tags

NGSS.HS-PS1-5

A student was asked to formulate a hypothesis about what would happen if 100. mL of 0.1 M NaOH(aq) at 25°C was combined with 100. mL of 0.1 M 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.

Tags

NGSS.HS-PS1-2

NGSS.HS-PS1-7

Reaction 2 occurs when an excess of 6 M HCl(aq) solution is added to 100. mL of NaOCl(aq) of unknown concentration. If the reaction goes to completion and 0.010 mol of Cl2(g) is produced, then what was the molarity of the NaOCl(aq) solution?

• 0.0010 M

• 0.010 M

• 0.10 M

• 1.0 M

The student claims that the reaction is an oxidation-reduction reaction. Which of the following statements correctly describes a change in oxidation number as the decomposition reaction proceeds?

• The oxidation number of hydrogen changes from +2 to +1.

• The oxidation number of hydrogen changes from +1 to +2.

• The oxidation number of oxygen changes from -2 to -1.

• The oxidation number of oxygen changes from -1 to 0.

Tags

NGSS.HS-PS1-7

Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125°C?

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Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-5

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. The following questions refer to the reactions represented below. A precipitation reaction

• H₂SeO₄(aq) + 2 Cl⁻(aq) + 2 H⁺(aq) → H₂SeO₃(aq) + Cl₂(g) + H₂O(l)

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

• Ca²⁺(aq) + SO₄²⁻(aq) → CaSO₄(s)

• PtCl₄(s) + 2 Cl⁻(aq) → PtCl₆²⁻(aq)

Tags

NGSS.HS-PS1-3