Unit 10 thermodynamics

Question 1

what are the steps to solve this problem: You have two identically prepared Styrofoam cups, each filled with the same volume of 20 ̊C water and a thermometer. (This arrangement is known as a“coffee cup calorimeter”.) Into cup #1, you drop 3.00 g of aluminum (c = 0.90 J/g∙K) that is heated to 80 ̊C. Into cup #2, you drop 3.00 g of iron (c = 0.45 J/g∙K)
that is heated to 80 ̊C. Which block (aluminum or iron) gives off more heat as it cools to the temperature of the water?

Answer 1

1. Calculate amount of heat given off by the aluminum block using the Q=mcdelta T formula
2. Calculate amount of heat given off by an iron using the Q=mcdelta T formula
3. pick the element that is more negative

Question 1

what are the steps to solve this problem: A layer of copper welded to the bottom of a skillet weighs 125 g.
How much heat is needed to raise the temperature of the
copper layer from 25°C to 300.°C? The specific heat capacity (c)
of Cu is 0.385 J/g∙K

Answer 1

1. Convert grams to kg
2. Find the change in temperature in kelvin
3. Use the formula for heat transfer Q=mcdeltaT isolated for Q. plug in the numbers and find the q value

Question 2

what are the steps to solve this problem:The temperature of the water in cup #1 increases from 20.0 ̊C to a final temperature of 28.2 ̊C as the aluminum cools?

Answer 2

1. simply subtract the final temperature from the initial temperature

Question 3

what is the purpose of calorimetry?

Answer 3

Measure the Heat of a Chemical or Physical Change

Question 4

how is heat measured in calorimetry?

Answer 4

indirectly by a calorimeter

Question 5

if a reaction produces heat, what happens to the temperature of its surroundings?

Answer 5

the temperature of the surroundings increases

Question 6

if a reaction absorbs heat, what happens to the temperature of its surroundings?

Answer 6

the temperature of the surroundings decreases

Question 7

what does coffee cup calorimetry mean?

Answer 7

used to measure enthalpy changes in chemical processes

Question 8

what are reactions and physical transformation like in calorimetry mean?

Answer 8

in an insulated container at constant pressure in a bath (usually water) of known heat capacity

Question 9

what is the significance of heat capacity?

Answer 9

provides a link between changes in temperature and heat gained
or lost, from which you can determine the enthalpy change of the system.

Question 10

what is the formula for finding heat capacity?

Answer 10

heat capacity=qcal/deltaTcal
where q cal is the amount of heat that must be added to the object to its temperature by delta T

Question 11

what are the steps to solve this problem: You heat up 22.05 g of a solid to 100.00 °C and add it to a “coffee cup” calorimeter which
contains 50.00 g water. The water temperature changes from 25.10 °C to 28.49 °C. Find the specific heat capacity of the solid.

Answer 11

1. Calculate heat gained by water using the formula Q=mcdeltaT and solving for q
   q=(50g4.184J/gC)(28.49-25.10)=710.7J
2. Calculate the heat lost by the solid which is equal to the heat gained by water qsolic=-qwater
   -710.7J
3. Calculate the change in temperature of the solid
   deltaT=100-28.49=71.51
4. Calculate the specific heat capacity
   c=-710.7J/22.05g71.51C)=0.449J/gC

Question 12

what are the two major types of calorimetry?

Answer 12

1. Constant Pressure or “Coffee Cup” Calorimetry
2. Constant Volume or “Bomb” Calorimetry:

Question 13

what is the formula for Constant Pressure or “Coffee Cup” Calorimetry?

Answer 13

qp = deltaE + PdeltaV

Question 14

what is the formula for Constant volume or “Coffee Cup” Calorimetry?

Answer 14

qv = deltaE + PdeltaV=deltaE

Question 15

which types of reactions are Bomb calorimeters are commonly used to
measure?

Answer 15

heat combustion reactions

Question 16

how is the heat flown into
the calorimeter and the heat of the reaction related?

Answer 16

qrxm=-qcalorimeter
they are them same of the qcalorimeter is negative

Question 17

what are the steps to solve this problem: When 0.500 g of ethanol, C2H6O, is burned in a bomb
calorimeter, the temperature of both the water and the calorimeter rise by 9.15oC. Assuming that the bath
contains 250.0 g of water and that the heat capacity for the calorimeter is 575 J/oC, calculate how much heat is created in this reaction?

Answer 17

1. Calculate heat absorbed by water
   Qwater in calorimeters=(mass of waterdeltaT)(cwater)
   qwater=(250g9.15C)(4.184L/g*K)=9571
2. Calculate heat absorbed by calorimeter
   qrxn=qcalorimeter=-[9571+575L/gK9.15C]=-14832J=-14.8
   kJ

Question 18

how do you solve a problem where you need to calculate deltaH (in kJ) for this rxn using two reactions lined up under the other?

Answer 18

1. cross out intermediates
2. rewrite the equation with whatever is left

Question 19

what happens to delta H when you reverse a reaction?

Answer 19

it turns negative

Question 20

what happens to delta H when you half a reaction?

Answer 20

you must also half delta H

Question 21

how to find the delta H for the summed of two reactions given their deltaH?

Answer 21

manipulate the two equations to get the desired equation while changing the delta H’s according. them add their delta H

Question 22

What is thermodynamics?

Answer 22

The study of energy and its conversion from one form to another