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CHM 142 +145 > CHM 145 final > Flashcards

CHM 145 final Flashcards

1
Q

properties that do not rely on the identity of the solution but rather how much of it is present

aka the concetration

A

Colligative properties

expt 1.

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2
Q

what does the addition of a non votile solute do to the vapor pressure of a solution?

expt. 1

A

it lowers the vapor pressure and therefore increases the boiling point

because the surface of the solution is more cluttered so less gas

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3
Q

change in boiling point =

expt. 1

A

molal boiling point constat * molality

Kbm

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4
Q

moles of solute/ kg of solvent * the number of ions the solute dissociates into

A

molality

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5
Q

did salt or sugar have the higher bp and why?

expt. 1

A

salt (NaCl) because it dissociates into ions (aka is an electrolyte) and sugar is nonpolar (nonelectrolyte) and does not dissolve

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6
Q

In the experiment you had to be sure that the 150mL beaker was covered to not let the solvent escape in large quantities, what would happen if you let the solvent escape freely?

expt. 1

A

The molality would be affected. this would raise the boiling point of the solution past the correct point.

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7
Q

what were the dependent and independent variables for expt. 1 Colligative properties?

aka what did you change and what did you measure/ x and y axis

A

dependant variable (y): temperature change
independent variable (x): substance (NaCl or sugar)

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8
Q

the change in concetration of reactants or products over the change in time

depends on the reactant concentrations

A

reaction rate

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9
Q

what can catalysts change about a reaction?

expt. 2

A

they can lower the Ea which increases the reaction rate

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10
Q

proteins that lower the activation energy and are not decomposed in reactions

expt. 2

A

catalysts

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11
Q

how do you convert from the Kpa/s to M/s

expt. 2

A

kpa/s/(8.314*TempK)

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12
Q

what is the rate law from the chemical kinetics expt. 2

A

R=k[H2O2}^x[KI]^y

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13
Q

the minium energy required to bring a reaction to completion

A

activation energy

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14
Q

how do you find Ea?

A

ln(k)=-Ea/RT+lnA

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15
Q

as concentration of H2O2 decreased what happened to the reaction rate?

A

the reaction rate also decreased

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16
Q

—- in a chemical reaction occurs when concentrations are stagnant but reactions do not stop occuring

aka the rate of the forward and the reverse reactions are =

A

equilibrium

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17
Q

what is the concetration of the products and the reactants goverend by?

A

the equilibrium constant (Keq)

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18
Q

Finish the hypothesis

if the concentration of Fe3+ is held constant and the concentration of SCN is increased the absorbance of the complex ion will—

A

increase

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19
Q

What is the equation for the ionization of acid in water?

A

HA+H2O—A- +H3O+

A: conjugate base

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20
Q

If you are shown a graph of pH (Y) and log([A-]/[HA]) how do you determine pKa?

A

by the y-intercept of the graph

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21
Q

Complete the hypothesis

I expect that test tube #—will have the highest pH bc—

A

Test tube #12 will have the highest pH because it had the highest concentration of the base HPO42-

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22
Q

If pH>pKA what color will the soln be?

A

the color of the basic form of the indicator

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23
Q

if pH<pKa what color will the soln be?

A

the color of the acidic form of the indicator

24
Q

for qualitative evaluation of the test tubes what will the pKa be?

A

The pKa will be = to the pH of the tube that has the most equal mixture of both the basic and the acidic form of the indicator by color

25
Q

absorbance is —- to concentration

A

proprotional

aka =

26
Q

When using derivatives to determine pKa what is the value of pKa?

A

the pH of the peak of the first derivative is the pKA

27
Q

what is Ai in the rearranged henderson hasselbalch equation?

hint: it does not stay consistent

A

it is the absorbance at each measurments pH

28
Q

what is Aa in the rearranged Henderson Hasselbalch equation?

hint: it stays consistent

A

the most acidic measurements absorbance

29
Q

What is Ab in the rearranged henderson hasselbalch equation?

hint: it stays consistnet

A

the most basic measruments absorbance

30
Q

how do Ai, Ab and Aa fit into the re-arranged henderson hasselbalch equation

A

pH= pKa +log (Ai-Aa/Ab-Ai)

31
Q

an aq. solution of a weak acid and its conjugate basae

A

Buffer

32
Q

What are three ways a buffer can be made?

A
  • adding a weak base to strong acid
  • adding weak acid to strong base
  • adding salt of an acid to the acid
33
Q

the capacity of the buffer to consume acid is limited by its concentration of —

A

base

A-

34
Q

the capacity of the buffer to consume base is limited by its concentration of —

A

acid

HA

35
Q

If the pKa of a buffer is 6.2 what would be a range the buffer would be effective in resisting change?

expt 5

A

5.2-7.2

36
Q

How do you calculate the expected buffer capacity? / what do you need to calculate it?

expt. 5

A

concentration of the base in the buffer and the amount of moles of acid needed to ‘break ‘ the buffer and volume of the buffer

37
Q

The extent to which a dissolution reaction occurs is dependent on the —- of the —-

expt 6

A

Magnitude, Ksp

38
Q

For a precipitate to form Q must be —- than Ksp

expt 6

A

larger

Q>Ksp

39
Q

True or false? the larger the pKsp value the harder it is to form a precipitate?

A

False, any pKsp value larger than 7 is easily formed and stable

40
Q

What is a flame test useful for finding?

A

If Na is present in a solution

41
Q

What is a Fe(salicyltate) test useful for finding?

expt 6

A

H2PO4-

42
Q

What is a AgNo3 test useful for finding?

expt 6

A

If a halide (Br, I, Cl-) are present in a solution

43
Q

What are acceptable places for collecting nitrate field samples?

expt 7

A

Pond, stream, river

44
Q

what device was used to determine voltage of the nitrate solutions?

expt 7

A

ISE (ion selective electrode)

45
Q

what were the x and y axis of the calibration curve used to determine nitrate concentration?

expt 7

A

x- axis: Log (concentration of nitrate)
y-axis: measured potential (mv)

46
Q

An electrochemical devices that allows for a redox reaction to occur spontaneously while transferring electrons externally

A

Voltaic cell

expt 8

47
Q

to be oxidized is to —

A

lose electrons

48
Q

to be reduced is to —

A

gain electrons

49
Q

electrons flow from the — to the —

A

anode, cathode

50
Q

how do you know which species is the cathode based on the standard potentials?

A

which ever one is most positive will be the cathode value

most negative will be anode value

51
Q

How do you calculate standard deviation?

A
  • take all the sample values and subtract the mean from them then square that value
  • add those squared values together and divide that by n-1
  • Take the dividie value and x^.5
52
Q

T-test equation for comparison to an accepted value

A

I u-meanI > t*Sm

t= n-1

53
Q

T-test equation for comparison of two values that have the same number of measurements

A

Im1-m2I> t(Sm1^2 +Sm2^2)^.5

t= 2n-2

54
Q

T-test equation for comparison of two values that have a different number of measruments

A

Imean1-mean2I>tS12((n1+n2)/’n1n2)^.5

t= n1+n2-2

55
Q

If the equality holds in a T-test what does this mean?

A

the values are statistically significant

CHM 142 +145 (6 decks)

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