Chapter 6- Thermochemistry

Question 1

Thermochemistry

Answer 1

The study of the relationship between chemistry and energy

Question 2

Energy

Answer 2

The capacity to do work

Question 3

Work

Answer 3

result of a force acting through a distance

Question 4

heat

Answer 4

flow of energy due to temperature difference

Question 5

kinetic energy vs thermal energy

Answer 5

kinetic energy is associated with the motion of an object and thermal energy is the energy associated with the temperature of an object. Thermal energy is a type of kinetic energy because the speed of atoms changes the overall temperature.

Question 6

Potential energy

Answer 6

is associated with the position or composition of an object

Question 7

chemical energy

Answer 7

energy associated with the position of electrons around the nuclei of atoms or molecules. (another form of potential energy)

Question 8

law of conservation of energy

Answer 8

energy can neither be created nor destroyed only transfered from one form to another

Question 9

explain the relationship between energy lost and energy gained by the system/surroundings?

Answer 9

the amount of energy lost is equal to the amount of energy gained

Question 10

What is the difference between a joule and calorie and a kcal?

Answer 10

joule is the standard unit for energy and is a relatively small unit, calorie is the amount of energy needed to raise the temperature of 1g of water by 1 degree celcius =4.184J, and a kcal is 1000 calories and 4184 joules (used on food labels)

Question 11

first law of thermodynamics

Answer 11

the energy of the universe is constant

Question 12

internal energy

Answer 12

sum of both kinetic and potential energies within a system, change. in internal energy is equal to the sum of the work done and the heat transfered.

Question 13

explain the chequing account analogy for energy tranfer from system to surroundings?

Answer 13

energy traveling into the system carries a positive sign, energy exiting the system carries a negative sign

Question 14

when looking at a chemical reation how does internal energy and energy of a reation differ?

Answer 14

the values will be the same, U of the products- U of the reactants will give you the same product as the sum of work and heat. U that is negative means more interal energy lays in the reatants and U positive menas more interna energy lays in the products

Question 15

Summarize energy flow

Answer 15

if the internal energy of a system is positive the products possess more energy than the reatants and energy flows into the system from the surroundings. is the internal energy of a system is negative then the reatants possess more internal energy and the energy flows from the system to the surroundings.

Question 16

explain the difference between heat capacity and specitfic heat capacity.

Answer 16

heat capacity is an extensive property (depends of the amount of matter being heated) whereas specific heat capacity is defined as the amount of heat need to heat 1g of a substance by 1 degree celcius therefore it is an intrinsic value.

Question 17

what equations can we used to calculate work?

Answer 17

w=-deltanRT (delta n is the number of moles of gas) w=-pdeltaV (where p is pressure and delta d represents the volume change)

Question 18

why do we use bomb calorimetry in chemistry?

Answer 18

measuring temperature change is easier, so by keeping a reaction under constant volume we eliminate work from the internal energy equation.

Question 19

explain bomb calorimetry?

Answer 19

bomb calorimeters are used for combustion reactions, the sample is placed a cup equipped with an ignition wire, the cup is placed into a sealed conatiner called a bomb to ensure it takes place at constant pressure. then the bomb is placed in a water filled insulated conatiner equipped with a stirrer and a thermometer, as the subtance burns the temperature is measured.

Question 20

Explain coffee cup calorimetry?

Answer 20

two styrofoam cups are placed into one another to stop heat from escaping, a stirrer and a thermometer are both inserted into the solution. Coffee cup calorimetry is used to measure temperature change in solution.

Question 21

Difference between coffee cup and bomb calorimetry?

Answer 21

coffee cup calorimetry measures change in enthaply at constant pressure and bomb calorrimetry mesures change in internal energy at constant volume.

Question 22

Explain Hess’s law?

Answer 22

The change in enthalpy for a stepwise process is the sum of the enthapy changes of the steps. if a reacion is multiplied enthaply is also multiplied, if a reaction is reversed the sign of enthaply flips, and the sum of all steps is the total enthaply.

Question 23

What is a standard state of formation?

Answer 23

1 mole of product is formed using elements/compounds in their standard states aka 1 bar/25 degrees.