chpater 10

Question 1

What is energy?

Answer 1

Energy is the capacity to do work.

Question 2

What is thermal energy?

Answer 2

Thermal energy is a type of kinetic energy associated with the motion of an object.

Question 3

What is chemical energy?

Answer 3

Chemical energy is the potential energy associated with the position and composition of electrons in atoms and molecules.

Question 4

What is the SI unit of energy?

Answer 4

The Joule (J) is the SI unit of energy.

Question 5

What is a calorie?

Answer 5

A calorie (cal) is the energy required to raise the temperature of 1 gram of water by 1 °C.

1 cal = 4.184 J

Question 6

What does the law of conservation of energy state?

Answer 6

The law of conservation of energy states that energy can be neither created nor destroyed.

Question 7

How can energy be transferred?

Answer 7

Energy can be transferred as heat or work.

Question 8

What is heat?

Answer 8

Heat is the flow of energy caused by a temperature difference.

Question 9

What is work?

Answer 9

Work is the result of a force acting through a distance.

Question 10

What is a system in thermodynamics?

Answer 10

The system is what is being studied.

Question 11

What are surroundings in thermodynamics?

Answer 11

The surroundings are everything with which the system can exchange.

Question 12

What does the first law of thermodynamics state?

Answer 12

According to the first law of thermodynamics, the total energy of the universe is constant.

Question 13

What is internal energy?

Answer 13

The internal energy (E) of a system is the sum of the kinetic and potential energies of all the particles that compose the system.

Question 14

What is the equation for change in internal energy?

Answer 14

ΔE = Efinal - Einitial = Eproducts - Ereactants.

Question 15

What does a negative ΔEsys indicate?

Answer 15

ΔEsys is negative indicates energy flows out of the system into the surroundings.

Question 16

What does a positive ΔEsys indicate?

Answer 16

ΔEsys is positive indicates energy flows into the system from the surroundings.

Question 17

What is the relationship between heat and internal energy?

Answer 17

The change in internal energy of the system is the sum of the heat transferred (q) and the work done (w).

ΔE = q + W

Question 18

What does it mean if q is positive?

Answer 18

If heat is absorbed by the system from the surroundings, q is positive (endothermic).

Question 19

What does it mean if q is negative?

Answer 19

If heat is transferred from the system to the surroundings, q is negative (exothermic).

Question 20

What does it mean if w is positive?

Answer 20

If work is done on the system by the surroundings, w is positive (volume decrease).

Question 21

What does it mean if w is negative?

Answer 21

If work is done by the system on the surroundings, w is negative (volume increase).

Question 22

What happens in a cylinder and piston assembly when warmed?

Answer 22

The contents of the cylinder expand, doing work on the surroundings by pushing the piston outward against the external pressure.

Question 23

How is work defined in terms of pressure?

Answer 23

Wsys = -PΔV (work = -pressure x change in volume)

Question 24

What is the formula for enthalpy (H) of a system?

Answer 24

H = E + PV

Question 25

How is enthalpy change (ΔH) expressed at constant pressure?

Answer 25

ΔH = ΔE + PΔV

Question 26

What is the relationship between ΔE, q, and w?

Answer 26

ΔE = q + w and w = -PΔV

Question 27

What does a positive ΔH indicate about a reaction?

Answer 27

A reaction with a positive ΔH is endothermic: it absorbs heat from its surroundings.

Question 28

What does a negative ΔH indicate about a reaction?

Answer 28

A reaction with a negative ΔH is exothermic: it gives off heat to its surroundings.

Question 29

What is heat capacity (C) of a system?

Answer 29

Heat capacity is the quantity of heat required to change its temperature by 1 °C.

Question 30

What is specific heat capacity (Cs)?

Answer 30

Specific heat capacity is the intrinsic capacity of a substance to absorb heat, measured in J/g • °C.

Question 31

What is the formula for calculating heat (q) for a specific material?

Answer 31

q = m × Cs × ΔT

Question 32

How is ΔT calculated?

Answer 32

ΔT = T2 - T1

Question 33

What is the reaction for producing hydrogen gas from methane and steam?

Answer 33

CH4 (g) + 2H2O(g) → 4H2(g) + CO2(g)

Question 34

What is the standard state of a gas?

Answer 34

The pure gas at 1 atm.

Question 35

What is the standard state of a liquid or solid?

Answer 35

The pure substance in its most stable form at 1 atm and the temperature of interest (usually 25 °C).

Question 36

What is the standard state of a substance in solution?

Answer 36

The substance in solution with a concentration of 1 M.

Question 37

What does ΔH° represent?

Answer 37

The change in enthalpy for a process when all reactants and products are in their standard states.

Question 38

What is the standard enthalpy of formation (ΔHf°) for a pure element in its standard state?

Answer 38

0.

Question 39

How is ΔHf° defined for a pure compound?

Answer 39

It is equal to the change in enthalpy when 1 mole of compound forms from its constituent elements in their standard states.

Question 40

What is the equation for calculating ΔH for a reaction?

Answer 40

ΔH = nΔHf° (products) - nΔHf° (reactants)