Lab Quiz #2 [Thermodynamics + Buffers]

Question 1

What is thermodynamics?

Give an example

Answer 1

• is the flow of energy in living system
• ex. chem. energy (E found in bonds)

Question 2

State the first law of thermodynamics

Give some examples

Answer 2

energy cannot be created or destroyed; can only be transformed from one state to another

ex. chem energy -> mech. energy
glucose -> muscle energy

Question 3

State the second law of thermodynamics

Answer 3

With each transformation, energy is lost as heat (not 100% transformed)

all living organisms require continue input of energy

Question 4

Describe an ENDERGONIC reaction

Answer 4

• requires input of E for rxn to proceed
• products contain more free E than reactants

Question 5

Describe an EXERGONIC reaction

Answer 5

• release E as rxn proceeds
• product contains less free E than reactants

Question 6

What type of reaction is this?

e + A + B -> C

Answer 6

endergonic rxn
(reactants are low e, product is high e)

Question 7

What type of reaction is this?

A + B -> C + e

Answer 7

exergonic rxn
(reactants are high E, product is low E)

Question 8

If E is released by ________ rxn, it may lead to running the ___________ rxn

Answer 8

exergonic

endergonic

Question 9

What ΔG sign means an EXERGONIC rxn?

What does it mean? What type of reaction is it?

Answer 9

-ΔG

negative

It means you are releasing E; spontaneous reaction

Question 10

What ΔG sign means an ENDERGONIC rxn?

What does it mean? What type of reaction is it?

Answer 10

+ΔG

positive

It means you are adding E to reactants; nonspontaneous rxn

Question 11

Can Rxn #1 run Rxn #2? Why or why not?

Rxn#1: ΔG = -100 cal
Rxn #2: ΔG = 25 cal

Answer 11

Rxn #1 CAN run rxn #2. This is because rxn #1 is releasing 100 cal of energy, and rxn #2 only requires 25 cal of energy to be ran.

Question 12

What happened to the temperature when KOH was added to water?

What type of reaction? Where did the energy go?

Is ΔG positive or negative?

Answer 12

The final solution temperature increased

Exergonic reaction; there was more energy in the bonds of the reactants than needed to make the product; therefore, when the bonds broke, energy was released in the form of heat (which is why the final solution temperature was warmer)

-ΔG (negative) because energy was released

Question 13

What happened to the temperature when NH4Cl was added to water?

What type of reaction? Where did the energy go?

Is ΔG positive or negative?

Answer 13

The final solution temperature decreased

Endergonic reaction; the energy in the bonds of the reactants was lower compared to the energy needed to create the product, thus more energy was needed to be inputted into the rxn

+ΔG (positive) because energy was inputted

Question 14

Describe what happened when barium hydroxide and ammonium thiocyanate were mixed together?

Was the energy found in the bonds of the original reactants greater or less than that found in the final products?

Exergonic or endergonic? Positive or negative ΔG?

Answer 14

The two solids were mixed which led to the transformation of a slush. The final temperature decreased, which means that heat was NOT released. The reaction must have taken in heat which is why the temperature decreased

The energy found in the bonds of the original reactants was less than in the products.

Endergonic reaction; +ΔG (positive)

Question 15

Define pH

Answer 15

measure of concentration of H ions in a solution in a log scale (power of 10); equals 1 * 10^-7

Question 16

What numbers on the pH scale indicate if a solution is acidic, neutral, or basic?

Answer 16

acidic - 1

neutral - 7

alkaline/basic - 14

Question 17

Which ion is measured with a pH meter?

Answer 17

H+ ions

Question 18

What does it mean if a solution is acidic?

Answer 18

more H+ present than OH-

Question 19

What does it mean if a solution is basic?

Answer 19

more OH- present than H+

Question 20

What does it mean if a solution is neutral?

Answer 20

H+ = OH-

Question 21

What is the normal range for blood pH?

How is this normal range maintained?

Answer 21

7.35 - 7.45

normal range is maintained through buffer; bicarbonate - HCO3

Question 22

When does acidosis occur?

Answer 22

pH < 7.35

Question 23

Define buffers

What are some common buffers?

Answer 23

molecules that slow changes in pH by combining with or releasing H+

protein, phosphate, bicarbonate

Question 24

Write the rxn for the bicarbonate system in blood

Answer 24

H20 + C02 - H2CO3 - H+ + HCO3-

Question 25

Which way will the reaction run if the blood is too basic?

H20 + C02 - H2CO3 - H+ + HCO3-

Answer 25

basic means more OH- than H+

reaction will run from left to right in order to release H+ ions. this will make the blood less basic and move toward homeostasis

Question 26

Which way will the reaction run if the blood is too acidic?

H20 + C02 - H2CO3 - H+ + HCO3-

Answer 26

acidic means more H+ than OH-

reaction will run from right to left. bicarbonate will combine with excess H+ ions, which will reduce the acidity of the blood.

Question 27

What happened when HCl was added to distilled H20?

What happened when HCl was added to a phosphate buffer?

Answer 27

pH decreased in larger increments (became more acidic)

pH still decreased but in smaller increments

Question 28

What happened when NaOH was added to distilled H20?

What happened when NaOH was added to a phosphate buffer?

Answer 28

pH increased in larger increments (became more basic)

pH still increased but in smaller increments