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Unit 9 – Concepts of Acids & BasesUnit 10 - Thermochemistry

Chemical Reactions

Got it all Acid AND ?

Enthalpy/Energy

EXO / ENDO

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Which of the following chemical reactions will produce a precipitate?

A. 3KBr + AlPO4 → K3PO4 + AlBr3

B. ZnCl2 + Mg2SO4 → ZnSO4 + MgCl2C. Na2CO3 + CaCl2 → CaCO3 + 2NaClD. NH4OH + KCl → KOH + NH4Cl

c

Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g)

Which of the following statements best explains why the chemical reaction shown above is an oxidation-reduction reaction?

F. Zn reacts under basic conditions.G. Zn dissolves in an aqueous solution.H. Zn and H+ undergo a change of state.J. Zn loses electrons and H+ gains electrons.

j

The reaction below shows carbon monoxide burning in oxygen.

2 CO + O2 → 2 CO2

What is the change in the oxidation number of carbon for this reaction?

A. +2 to +1B. +2 to +4C. +4 to +1D. +4 to +2 b

Copper (II) nitrate and sodium hydroxide solutions react in a test tube as shown below.

Cu(NO3)2(aq) + 2NaOH(aq)→ Cu(OH)2(s) + 2NaNO3(aq)

If nitric acid is added to the test tube, the amount of solid precipitate decreases. The best explanation for this is that the acid-

F. Will dissolve most solids, including sodium nitrate.G. Dilutes the solution making the precipitate dissolve.H. Reacts with the copper (II) nitrate, pulling the equilibrium to the left.J. Will react with the copper (II) hydroxide to form water and soluble copper(II) nitrate.

j

Consider this balanced chemical equation:

Zn (s) + 2 HCl (aq) → ZnCl2 (aq) + H2 (g)

Which is the oxidation half-reaction?

A. Zn → Zn2+ + 2e-

B. Zn + 2e- → Zn2+

C. 2H+ → H2 + 2e-

D. 2H+ + 2e- → H2

A

Which of the following reaction shows an acid-base reaction?

F. Na2CO3 + CaCl2 → CaCO3 + 2NaClG. HCl + NaOH → H2O +NaClH. CH4 + O2 → CO2 + H2OJ. Mg +HCl → MgCl2 + H2

g

What is the pH of a substance with 6.0 × 10–8 M [H3O+]?

F. 1.89G. 2.63H. 4.90J. 7.22

j

Grapefruit juice has a pOH of approximately 11.0. What is the pH of grapefruit juice?

A. 3.0B. 5.0C. 9.0D. 11.0

a

A solution of a metal hydroxide is prepared by placing 1 mole of the compound in water and stirring. Less than 1% of the solid dissolves. Which of the following is the most likely value of the pH of the solution?

A. 1B. 6C. 8D. 14

c

10. Which energy conversion occurs during the operation of an electrolytic cell?

A. Chemical energy to electrical energyB. Electrical energy to chemical energyC. Nuclear energy to electrical energyD. Electrical energy to nuclear energy

b

An 18.0 g piece of an unidentified metal was heated from 21.5°C to 89.0°C. If 292 J of heat energy was absorbed by the metal in the heating process, what was the identity of the metal?

F. CalciumG. CopperH. SilverJ. Iron

h

Which energy conversion occurs during the operation of an electrolytic cell?

A. Chemical energy to electrical energyB. Electrical energy to chemical energyC. Nuclear energy to electrical energyD. Electrical energy to nuclear energy

b

Which of the following is one of the products of the reaction between sulfuric acid and sodium hydroxide?

F. Sodium hydrideH. Sulfur dioxideG. Sodium sulfateJ. Hydrogen

g

The diagram below shows the structure of a common pain reliever.

Which of the highlighted atoms or group of atoms makes aspirin a Brønsted-Lowry acid?

F. 1G. 2H. 3J. 4

g

In the reaction represented by this equation, which substance(s) act as a Brønsted-Lowry acid?

CH3COOH + H2O H3O+ + CH3COO

A.H2O onlyB. CH3COOH onlyC. CH3COOH and H3O+

D. H2O and CH3COOC

c

Hydrochloric acid is a strong acid. How will it dissociate in water?

F. It will partially dissociate in water.G. It will fully dissociate in water.H. It will not dissociate in water.J. It will not mix with water.

g

As a rock rolls down a hill, its potential energy is converted into kinetic energy, sound energy, and even thermal energy. What is true about the total energy of this system?

A. Energy is lost as the rock moves down the hill.B. Energy is gained as the rock moves down the hill.C. The total energy remains the same as the rock moves down the hillD. The total energy is constantly changing as the rock moves down the hill.

C

The temperature of a sample of water changes from 10°C to 20°C when the sample absorbs 418 joules of heat. What is the mass of the sample?

F. 100 gG. 10 gH. 1000 gJ. 1 g

g

Which enthalpy diagram shows that the reaction A2(g) + X2(g) → 2AX(g) is an exothermic reaction that produces 550 kJ of heat?

A. B.

C. D.

A

For the reaction shown below, calculate the enthalpy of reaction for decomposition of hydrogen peroxide into oxygen and water and determine if the reaction is exothermic or endothermic.2H2O2(l) → O2(g) + 2H2O(g)

ΔHf of reactants: ΔHf H2O2 (l) =-187.8 kJ/molΔHf of products: ΔHf O2 (g) = 0.00 kJ/molΔHf H2O(g) =-285.8 kJ/mol

F. 196 kJ/mol, endothermicG. -196 kJ/mol, exothermicH. 474 kJ/mol, exothermicJ. -474 kJ/mol, endothermic

g

In the figure of molecules shown below, what is occurring?

A.Energy is removed from a solid to form a liquid.

B. Energy is removed from a liquid to form a solid.C. Energy is added to a solid to form a liquid.D. Energy is added to a liquid to form a solid. c

How do you set up the enthalpy change for the reaction shown below?

C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (l)

Enthalpies: C2H4 (g) = 52.26 kJ/molO2 (g) = 0 kJ/molCO2 (g) = –393.5 kJ/molH2O (l) = –285.8 kJ/mol

F. [2(–393.5 kJ/mol) + 2(–285.8 kJ/mol)]– [(52.26 kJ/mol) + 3(0 kJ/mol)]G. –[2(–393.5 kJ/mol) + 2(–285.8 kJ/mol)]– [(52.26 kJ/mol) + 3(0 kJ/mol)]H. [(52.26 kJ/mol) + 3(0 kJ/mol)] +[2(–393.5 kJ/mol) +

2(–285.8 kJ/mol)]J. [(52.26 kJ/mol) + 3(0 kJ/mol)] –[2(–393.5 kJ/mol) +

2(–285.8 kJ/mol)] f

As heat is slowly added to a glass of ice water, the temperature remains at 0°C. Which of the following statements explains why the temperature of the mixture of ice and water remains constant as heat is added?

A. Heat is stored in the solid ice.B. Heat is stored in the liquid water.C. Heat is used to turn the solid ice into liquid water.D. Heat is absorbed equally by the solid ice and the liquid water.

c

The diagram below shows a heating curve for a substance. Between points X and Y, which of the following would be observed?

A.Solid and liquid will be present as the temperature remains constant.B. Liquid and vapor will be present as the temperatureremains constant.C. Only vapor will be presentas the temperature gradually increases.D. Only liquid will be present as the temperature gradually increases.

B

Which of the following statements describes all exothermic reactions?

F. Exothermic reactions form gases.G. Exothermic reactions require a catalyst.H. The energy of the reactants is lower than the energy of the products.J. The energy of the reactants is higher than the energy of the products.

j

Black powder has been used as a propellant for fireworks for centuries. One of the components of black powder is potassium nitrate (KNO3). A sample of black powder containing 1 mol of KNO3 releases 289 kJ of heat during combustion. The molar mass of KNO3 is 101 g/mol. How much heat is released if a firework contains 250 g of KNO3?

A. 117 kJB. 715 kJC. 29,189 kJD. 72,250 kJ b

A sample was burned in a calorimeter that has a 3000 mL water bath. The temperature of the water rose from 22°C to 46°C. How much heat was produced by the reaction? (Specific heat of water is 4.184 J/gK)

A. 301 JB. 12.5 kJC. 301 kJD. 577 kJ

c

Which equation represents an exothermic reaction at 298 K?

A. N2(g) + O2(g) → 2NO(g)B. C(s) + O2(g) → CO2(g)C. KNO3(s) → K+(aq) + NO3-(aq)D. NH4Cl(s) → NH4+(aq) + Cl-(aq)

b

Given the balanced equation representing a phase change:

C6H4Cl2 (s) + energy → C6H4Cl2 (g)

Which statement describes this change?

F. It is endothermic, and entropy decreases.G. It is endothermic, and entropy increases.H. It is exothermic, and entropy decreases.J. It is exothermic, and entropy increases..

g

Which is always true of an endothermic reaction?

A. Chemical bonds are broken.B. Energy is absorbed.C. Energy is released.D. Light is created.

B