Review for Unit7 Chemical Reactions

What do these equation symbols mean?

• dissolved in water

• -->

• liquid

• (s)

• yields

• (g)

• gas

• (l)

• solid

• (aq)

Correctly identify these polyatomic ions

• NO₂^-

• ammonium

• NH₄⁺

• sulfate

• NO₃^-

• nitrate

• OH^-

• nitrite

• SO₄^2-

• hydroxide

The reaction between solid aluminum and liquid bromine is exothermic. This reaction creates the product aluminum bromide. What equation includes the correct formulas and demonstrates conservation of mass?

• Al(s) + Br₂(l) → AlBr₃(s)

• Al(s) + Br(l) → AlBr(s)

• Al(s) + 3Br(l) → AlBr₃(s)

• 2Al(s) + 3Br₂(l) → 2AlBr₃(s)

Answer explanation

solid aluminum is Al³⁺

liquid bromine is Br₂

Tags

NGSS.HS-PS1-7

Students perform an experiment that instantaneously forms a precipitate. They mix aqueous iron (III) nitrate and sodium hydroxide to produce iron (III) hydroxide and aqueous sodium nitrate. What is the correct balanced equation for this reaction to show conservation of mass?

• 3FeNO₃ + 2NaOH → FeOH₃ + 3NaNO₃

• FeN + 3NaOH → FeOH₃ + 3NaN

• Fe(NO₃)₃ + 3NaOH → Fe(OH)₃ + 3NaNO₃

• Fe³⁺NO₃⁻ + Na⁺OH⁻ → Fe³⁺OH⁻ + Na⁺NO₃⁻

Answer explanation

iron (III) is Fe³⁺

nitrate is NO₃^-

sodium is Na⁺

hydroxide is OH^-

Tags

NGSS.HS-PS1-7

NGSS.HS-PS1-2

What are the coefficients that would correctly balance this equation?

Zn +​ ​ K₂CrO₄ ⟶​ (a)   K +​ (b)   ZnCrO₄

• 3
• 0.5
• 2
• 1

Tags

NGSS.HS-PS1-7

In the reaction 2H₂ + O₂ → 2H₂O, what is the mole ratio of hydrogen to water?

• 2 : 2

• 2 : 1

• 1 : 2

• 4 : 4

Tags

NGSS.HS-PS1-7

In the reaction 2RbNO₃ → 2RbNO₂ + O₂, how many moles of O₂ are produced when 5.0 mol of RbNO₃ decompose?

• 1.0 mol

• 2.5 mol

• 3.0 mol

• 7.5 mol

Answer explanation

Based on the balanced equation

2RbNO₃ → 2RbNO₂ + O₂

the molar ratio of RbNO₃ to O₂ is 2:1 which means that every 1 mole of RbNO₃ will produce 0.5 moles of O₂

Tags

NGSS.HS-PS1-7

Calcium hydroxide and hydrochloric acid react to form calcium chloride and water as shown in the chemical reaction. If the chemicals are present in exactly the correct ratios to fully use all of the ingredients, how many moles of water would be formed from 5 moles of HCl?

___Ca(OH)₂ + ___HCl → ___CaCl₂ + ___H₂O

(a)  

• 1 mole

• 2 moles
• 10 moles

• 5 moles

Answer explanation

The balanced equation is

1 Ca(OH)₂ + 2 HCl → 1 CaCl₂ + 2 H₂O

which means that molar ratio of HCl to H₂O is a 2:2 ratio, or rather a 1:1 ratio.

Tags

NGSS.HS-PS1-7

By predicting the outcome of the following reactants mixing together in an aqueous solution, what type of reaction will take place?

Pb(NO₃)₂ (aq) + 2 KI (aq) →

• Double-replacement reaction

• Synthesis reaction

• Decomposition reaction

• Single-replacement reaction

Which equation represents a neutralization reaction?

• H₂CO₃ (aq) → CO₂ (g) + H₂O (l)

• H₂SO₄ (aq) + 2NaOH (aq) → Na₂SO₄ (aq) + 2H₂O (l)

• 2H₂ (g) + O₂ (g) → 2H₂O (l)

• AgNO₃ (aq) + NaOH (aq) → AgOH (s) + NaNO₃ (aq)

Answer explanation

Neutralization takes the form of

HA + BOH --> AB + H₂O

which is acid + base --> salt + water