First Law of Thermodynamics

Multiple Choice

The Law of <blank> states that energy cannot be created nor destroyed only transferred

• Specific Heat

• Exothermic Reaction

• Conservation of Energy

• Potential Energy

Multiple Choice

The Law of Conservation of Energy is also known as...

• First Law of Thermodynamics

• Second Law of Thermodynamics

• Third Law of Thermodynamics

• Newton's First Law

Multiple Choice

The change in the energy between a chemical reaction and the surroundings at constant temperature is called

• enthalpy change

• enthalpy

• enthalpy profile

• dynamic enthalpy

Multiple Choice

The heat of reaction refers to

• The heat released after burning 1 mole of a substance.

• The amount of heat needed to melt 1 mole of a solid.

• The heat released by 1 mole of a substance as it changes from a liquid to a solid.

• The heat released or absorbed during a chemical reaction.

Multiple Choice

Changes in enthalpy in an exothermic reaction is

• Positive

• Negative

• Constant

• Neutral

Multiple Choice

A reaction is allowed to take place in an insulated container containing 100mL of water. If the reaction is exothermic, what happens to the temperature of water?

• The temperature of the water goes down.

• The temperature of the water goes up.

• The temperature of the water does not change.

• None of the above.

Multiple Choice

Which of the following does NOT describe an endothermic reactions?

• absorption of energy

• ΔH > 0

• H_reactant < H_product

• -ΔH

Multiple Choice

Given the hypothetical thermochemical equation:

A + B → C + D ΔH = -430 kJ/mol

Which among the following statements is correct about this reaction?

• The equation may be written as

  A + B $$\rightarrow$$ C + D

  $$\Delta$$ H=430 kJ/mol

• The reaction is exothermic.

• The heat content of C and D is greater than the heat content of A and B.

• The heat content of A and C is greater than the heat content of B and D.

Multiple Choice

The thermochemical equation showing the formation of ammonia (NH3) from its elements is:

N₂(g) + 3H₂(g) → 2NH₃(g) ΔH = -92 kJ/mol

This equation shows that 92 kJ of heat is:

• Lost to the surroundings when one mole of hydrogen is used up in the reaction.

• Absorbed from the surroundings when one mole of nitrogen reacts.

• Absorbed from the surroundings when one mole of ammonia is formed.

• Lost to the surroundings when 2 moles of ammonia is formed.

Multiple Choice

ΔH is expressed in units of

• cal

• kJ/mol

• J

• kcal

Multiple Choice

The standard condition for enthalpy changes is/are

• the pressure of 1 atm

• normal physical state

• temperature 298K

• all of these

Multiple Choice

An oxyacetylene torch is a tool that mixes and burns oxygen and acetylene to produce an extremely hot flame. This tool is used to cut steel or weld iron and other metals. The temperature of the film can reach 3480˚C. The burning of acetylene is given by the thermochemical equation:

C₂H₂(g) + 1½CO₂(g) → CO₂(g) + H₂O(l)    ΔH = -1301.1 kJ/mol

  For the reaction,

2CO₂(g) + 2H₂O(l) → 2C₂H₂(g) + 3CO₂(g)

  What is the ΔH for the reaction?

• ΔH = +1301.1 kJ/mol

• ΔH = +2602.2 kJ/mol

• ΔH = -1301.1 kJ/mol

• ΔH = -2602.2 kJ/mol

Multiple Choice

Solving for ΔH involves

• Reversing all given chemical reactions.

• Manipulating the equation so that the reactants and products are on the desired side of the equation

• Change the sign of ΔH

• Removing all reactants that are on the same side of the equation

EVALUATION

Multiple Choice

The variations in enthalpy that can not be detected per calorimeter can be detected with the aid of

• Newton’s law

• Krebs law

• Hess’s law

• Ohm’s law

Multiple Choice

Changes in enthalpy in an exothermic reaction is

• Positive

• Negative

• Constant

• Neutral

Multiple Choice

The change in the energy between a chemical reaction and the surroundings at constant temperature is called

• enthalpy change

• enthalpy

• enthalpy profile

• dynamic enthalpy

Multiple Choice

Given the hypothetical thermochemical equation:

A + B → C + D ΔH = -430 kJ/mol

Which among the following statements is correct about this reaction?

• The reaction is exothermic.

• The equation may be written as A + B → C + D 430 kJ/mol

• The heat content of C and D is greater than the heat content of A and B.

• The heat content of A and C is greater than the heat content of B and D.

Multiple Choice

The thermochemical equation showing the formation of ammonia (NH3) from its elements is:

N₂(g) + 3H₂(g) → 2NH₃(g) ΔH = -92 kJ/mol

This equation shows that 92 kJ of heat is:

• Lost to the surroundings when one mole of hydrogen is used up in the reaction.

• Absorbed from the surroundings when one mole of nitrogen reacts.

• Absorbed from the surroundings when one mole of ammonia is formed.

• Lost to the surroundings when 2 moles of ammonia is formed.

Multiple Choice

An oxyacetylene torch is a tool that mixes and burns oxygen and acetylene to produce an extremely hot flame. This tool is used to cut steel or weld iron and other metals. The temperature of the film can reach 3480˚C. The burning of acetylene is given by the thermochemical equation:

C₂H₂(g) + 1½CO₂(g) → CO₂(g) + H₂O(l)    ΔH = -1301.1 kJ/mol

  For the reaction,

2CO₂(g) + 2H₂O(l) → 2C₂H₂(g) + 3CO₂(g)

  What is the ΔH for the reaction?

• ΔH = +1301.1 kJ/mol

• ΔH = +2602.2 kJ/mol

• ΔH = -1301.1 kJ/mol

• ΔH = -2602.2 kJ/mol

Multiple Choice

The standard condition for enthalpy changes is/are

• the pressure of 1 atm

• normal physical state

• temperature 298K

• all of these

Multiple Choice

The heat of reaction refers to

• The heat released after burning 1 mole of a substance.

• The amount of heat needed to melt 1 mole of a solid.

• The heat released by 1 mole of a substance as it changes from a liquid to a solid.

• The heat released or absorbed during a chemical reaction.

Multiple Choice

The Law of <blank> states that energy cannot be created nor destroyed only transferred

• Specific Heat

• Exothermic Reaction

• Conservation of Energy

• Potential Energy