Topic: Chemical Reactions And Equations
Chemical Reactions And Equations
Which equation represents conservation of charge?
(1) I− + 2e− → I2
(2) 2I− → I2 + 2e−
(3) Br2 → 2Br− + 2e−
(4) Br + 2e− → Br−
Which equation represents a conservation of atoms?
(1) 2Fe + 2O2 → Fe2O3
(2) 2Fe + 3O2 → Fe2O3
(3) 4Fe + 2O2 → 2Fe2O3
(4) 4Fe + 3O2 → 2Fe2O3
During all chemical reactions, charge, mass and energy are
(1) condensed
(2) conserved
(3) decayed
(4) decomposed
Which quantities are conserved in all chemical reactions?
(1) charge, pressure, and energy
(2) charge, mass, and energy
(3) volume, pressure, and energy
(4) volume, mass, and pressure
Which equation shows conservation of mass and energy for a reaction at 101.3 kPa and 298 K?
(1) 2H2(g) + O2(g) → 2H2O(g) + 483.6 kJ
(2) 2H2(g) + O2(g) → 2H2O(ℓ) + 285.8 kJ
(3) H2(g) + O2(g) → H2O(g) + 483.6 kJ
(4) H2(g) + O2(g) → H2O(ℓ) + 285.8 kJ
What is conserved during all chemical reactions?
(1) charge
(2) density
(3) vapor pressure
(4) melting point
Which equation shows conservation of charge?
(1) Cu + Ag+ → Cu2+ + Ag
(2) Mg + Zn2+ → 2Mg2+ + Zn
(3) 2F2 + Br− → 2F− + Br2
(4) 2I− + Cl2 → I2 + 2Cl−
Given the balanced equation representing a reaction occurring at 101.3 kilopascals and 298 K:
2H2(g) + O2(g) → 2H2O(ℓ) + energy
What is the net amount of energy released when one mole of H2O(ℓ) is produced?
(1) 241.8 kJ
(2) 285.8 kJ
(3) 483.6 kJ
(4) 571.6 kJ
In 1828, Friedrich Wöhler produced urea when he heated a solution of ammonium cyanate. This reaction is represented by the balanced equation below.
Explain why this balanced equation represents a conservation of atoms.
Allow 1 credit. Acceptable responses include, but are not limited to:
• There are the same number of atoms of each element on both sides of the equation.
• No atoms are lost or gained.
In a laboratory investigation, a student constructs an electrochemical cell to decompose water, as represented in the diagram below. The water in the electrochemical cell contains a small amount of dissolved sodium sulfate, to increase conductivity. The three equations represent the reaction in each test tube and the overall reaction. During this laboratory activity, appropriate safety equipment is used and safety procedures are followed.
Determine the number of moles of hydrogen gas produced when 0.0004 mole of oxygen gas is produced in the cell by the overall reaction.
Allow 1 credit for 0.0008 mol or 8 × 10−4 mol. Significant figures do not need to be shown.
A metal worker uses a cutting torch that operates by reacting acetylene gas, C2H2(g), with oxygen gas, O2(g), as shown in the unbalanced equation below.
C2H2(g) + O2(g) → CO2(g) + H2O(g) + heat
Balance the equation in your answer booklet for the reaction of acetylene and oxygen, using the smallest whole-number coefficients.
Allow 1 credit for
• 2
• 5
• 4
• 2 _________ C2H2(g) + _________ O2(g) → _________ CO2(g) + _________ H2O(g) + heat
Automobile catalytic converters use a platinum catalyst to reduce air pollution by changing emissions such as carbon monoxide, CO(g), into carbon dioxide, CO2(g). The uncatalyzed reaction is represented by the balanced equation below.
2CO(g) + O2(g) → 2CO2(g) + heat
Determine the number of moles of O2(g) required to completely react with 28 moles of CO(g) during this reaction.
Allow 1 credit for 14 mol.
In a laboratory investigation, an HCl(aq) solution with a pH value of 2 is used to determine the molarity of a KOH(aq) solution. A 7.5-milliliter sample of the KOH(aq) is exactly neutralized by 15.0 milliliters of the 0.010 M HCl(aq). During this laboratory activity, appropriate safety equipment is used and safety procedures are followed.
Complete the equation below by writing the chemical formula for each product.
Allow 1 credit. Acceptable responses include, but are not limited to:
• KCl(aq) + H2
•
During a laboratory activity, appropriate safety equipment was used and safety procedures were followed. A laboratory technician heated a sample of solid KClO3 in a crucible to determine the percent composition by mass of oxygen in the compound. The unbalanced equation and the data for the decomposition of solid KClO3 are shown below.
Balance the equation below for the decomposition of KClO3, using the smallest whole-number coefficients.
Allow 1 credit for:
• 2 KClO3(s) → 2 KCl(s) + 3 O2(g).
The balanced equation below represents the reaction between carbon monoxide and oxygen to produce carbon dioxide.
2CO(g) + O2(g) → 2CO2(g) + energy
Determine the number of moles of O2(g) needed to completely react with 8.0 moles of CO(g).
Allow 1 credit for 4.0 mol or 4 mol.