1. Use the table to answer the question:

Bond Bond Energy
H–H 432
Br–Br 193
I–I 149
H–Br 363
H–I 295
Hydrogen bromide breaks down into diatomic hydrogen and bromine via the following reaction:
2HBr → H2 + Br2
Hydrogen iodide is formed from diatomic hydrogen and iodine via the following reaction:
H2 + I2 → 2HI
Are these reactions exothermic or endothermic?
(1 point)
A. Both reactions are exothermic.
B. The breakdown of hydrogen bromide is exothermic, and the formation of hydrogen iodide is endothermic.
C. The breakdown of hydrogen bromide is endothermic, and the formation of hydrogen iodide is exothermic.
D. Both reactions are endothermic.
2. Use the chemical equation and the bond diagram to answer the question.
2H2 + O2 → 2H2O
2H–H + O=O → 2H–O–H
The energy of the H–H bond is 432 kJ/mol. The energy of the O=O bond is 498 kJ/mol. The energy of the O–H bond is 467 kJ/mol.
Which bond is the weakest?
O–H
O–O
H–H
O=O
3.Use the reaction and bond information to answer the question.
H2 + CO2 → CH2O2
Reactant bond energies: H–H is 432 kJ/mol, C=O is 799 kJ/mol
Product bond energies: C–H is 413 kJ/mol, C=O is 745 kJ/mol, C–O is 358 kJ/mol, O–H is 467 kJ/mol
Is this system endothermic or exothermic, and why?
A. It is endothermic because more energy is given off by the products versus the amount needed to break up the reactants.
B. It is exothermic because more energy is given off by the products versus the amount needed to break up the reactants.
C. It is endothermic because more energy is needed to break up the reactants versus the amount given off by the products.
D. It is exothermic because more energy is needed to break up the reactants versus the amount given off by the products.
4. Use the table to answer the question.
Compound Electronegativity Difference
CO 0.89
NaCl 2.23
NO 0.04
CaBr 1.96
Which compound is most likely to be held together by a covalent bond based on the electronegativity difference between its two atoms?
A. CaBr
B. CO
C. NO
D. NaCl
5.Use the table of information about bond energies to answer the question.
Bond Energy (kJ/mol)
C–Cl 339
C–F 485
H–Cl 427
H–F 565
Which bond is more stable?
A. H–F
B. H–Cl
C. C–Cl
D. C–F
6. Which option is an example of energy transfer via radiation?(1 point)
A. a hot air balloon rising
B. sunlight warming a concrete sidewalk
C. melting ice in your hand
D. using a heating pad to warm stiff muscles
7. A closed system includes a cup of warm water and an ice cube that was just placed inside of it. Which statement describes the energy of the system over time?(1 point)
A. The total energy of the system will stay the same as kinetic energy from the warm water decreases the kinetic energy of molecules in the ice.
B. The total energy of the system will stay the same as kinetic energy from the warm water increases the kinetic energy of molecules in the ice.
C. The total energy of the system will decrease as the warm water causes the ice molecules to lose kinetic energy.
D. The total energy of the system will decrease as the ice causes the warm water molecules to lose kinetic energy.
8. The diagram shows that the potential energy of the products is lower than the potential energy of the reactants. Which type of reaction is shown?
A. This is an endothermic reaction because the reactants have more energy than the products.
B. This is an exothermic reaction because the reactants have more energy than the products.
C. This is an exothermic reaction because the reactants have less energy than the products.
D. This is an endothermic reaction because the reactants have less energy than the products.
9. What is activation energy?(1 point)
A. the energy that must be added to a system to break the bonds of the reactants
B. the kinetic energy of the reactants of a system after the reaction has begun
C. the total potential energy of the bonds of the reactants in a system
D. the energy released when atomic bonds are broken
10. Manganese dioxide acts as a catalyst in the decomposition of H2O2 into water and oxygen gas. Which statement best describes this function?(1 point)
A. The activation energy required for manganese dioxide to form intermediate molecules with H2O2 is less than the activation energy required for H2O2 to decompose on its own.
B. Manganese dioxide adds heat to the system so that the molecules of H2O2 collide with more force and are more likely to result in broken atomic bonds.
C. Manganese dioxide lowers the potential energy of the bonds in H2O2 so that less activation energy is required for H2O2 to decompose.
D. The potential energy of the bonds in manganese dioxide is less than the potential energy of the bonds in water and oxygen gas, so the activation energy is lower in the presence of manganese dioxide.