Chem 14BL week 1-4

Question 1

What is accuracy?

Answer 1

the closeness of a result to the true value

Question 2

What is precision

Answer 2

the closeness of a set of results to each other; reproducibility of a result; number of significant figures in a result

Question 3

What are significant figures?

Answer 3

any nonzero digit from 1-9; zeros between nonzero digits; ending zeros after a nonzero number with a decimal point

Question 4

In addition or subtraction, how many number of decimal places in the answer ?

Answer 4

the smallest number of decimal places in the data

Question 5

In multiplication or division, the number of significant figures in the answer

Answer 5

the smallest number of significant figures in the data

Question 6

When taking the log of a number, how many number of decimal places in the answer?

Answer 6

the number of significant figures of the number in the log

Question 7

When taking the antilog of a number, how many number of significant figures in the answer?

Answer 7

the number of decimal places of the exponent in the antilog

Question 8

Standard deviation formula?

Answer 8

the square root of the sum of the difference between each entry and the mean squared all over the number of entries

Question 9

Average deviation formula?

Answer 9

the sum of the absolute value of the difference of each individual number and the mean all over the number of entries

Question 10

Percent relative average deviation?

Answer 10

the average deviation divided by the mean multiplied by 100

Question 11

Absolute error?

Answer 11

expresses the margin of uncertainty associated with the measurement; represented by delta; has units

Question 12

Relative error?

Answer 12

also known as percent error, inherent error, or precision; compares the size of the absolute uncertainty with the size of its associated measurement; represented by absolute error divided by the measured quantity; no units

Question 13

Addition or subtraction of absolute error?

Answer 13

change of C equals change of A plus change of B

Question 14

Multiplication or division of absolute error?

Answer 14

change of C equals parantheses change of A divided by A plus change of B divided by B end parantheses multiplied by C

Question 15

Addition or subtraction of relative error?

Answer 15

change of C over C equals change of A divided by C plus change of B divided by C

Question 16

Multiplication or division of relative error?

Answer 16

change of C over C equals change of A divided by A plus change of B divided by B

Question 17

percent RAD is less than or equal to percent Inherent Error

Answer 17

experiment was performed within the precision warranted by the equipment; no need to repeat the experiment

Question 18

percent RAD is greater than percent Inherent error

Answer 18

experiment was not performed within the precision warranted by the equipment; experiment should be repeated

Question 19

spectrophotometric analysis

Answer 19

measuring the concentration of solutes in solution by measuring the amount of light that is absorbed by the solution in a cuvette placed in the spectrophotometer

Question 20

Beers Law?

Answer 20

A equals epsilon, L, C. epsilon depends on wavelength and identity of chemical species. L is in cm. c is the concentration of the colored substance usually in mol/L.

Question 21

Blank solution

Answer 21

a solution that contains all the chemical species except the one you want to measure. Purpose is to eliminate background interference

Question 22

Standard solution

Answer 22

a solution with a precisely known concentration. purpose is to create a Beer’s Law calibration plot

Question 23

Beer’s Law limitations

Answer 23

solution has a low concetration; absorbance range between 0.1 and 1.0; colored solutions; no reaction between species involved; alpha must be fixed during sample analysis; epsilon must be constant

Question 24

Absorption Spectrum

Answer 24

plots absorbance versus wavelength. the optimal wavelength corresponds to the maximum absorbance

Question 25

Why use optimal wavelength to plot Beer's Law Calibration graph?

Answer 25

maximize sensitivity of spectrophotometer; maximize slope of Beer's Law Calibration Plot; minimize error of spectrophotometer

Question 26

Beer's Law Calibration Plot

Answer 26

plots absorbance versus concentration at a specific wavelength; a minimum of three points are needed for a Beer's law graph; when Beer's Law is followed, the absorbance is directly proportional to the concentration

Question 27

the color absorbed is complementary to the color transmitted: true or false

Answer 27

true

Question 28

parts per million (ppm)

Answer 28

mg of solute / L of solution

Question 29

parts per billion (ppb)

Answer 29

micrograms of solute / L of solution

Question 30

weight per volume percent (w/v%)

Answer 30

g of solute/ 100 mL of solution

Question 31

molarity (M)

Answer 31

mol of solute (n) / L of solution (v)

Question 32

normality (N)

Answer 32

equivalents of H+ / L of solution --OR-- equivalents of OH- / L of solution

Question 33

What is equilibrium?

Answer 33

state in which chemical activities or concentrations of the reactants and products have no net change overt time

Question 34

Acid? Base? Conjugate Acid? Conjugate Base?

Answer 34

proton donor proton acceptor species formed when base accepts a proton species left when acid donates a proton

Question 35

strong vs weak acid/base

Answer 35

dissociates completely/ partially dissociates in aqueous solution

Question 36

Equilibrium Constant (K)

Answer 36

determines the extent of the reaction (whether it lies to the left or right side of the equation)

Question 37

relationship between K, pK, and acid/base

Answer 37

the smaller the value of the K(a), the greater the value of pK(a) and the weaker the acid the smaller the value of K(b), the greater the value of pK(b) and the weaker the base

Question 38

relationship between K, pK, and acid/base

Answer 38

the smaller the value of the K(a), the greater the value of pK(a) and the weaker the acid the smaller the value of K(b), the greater the value of pK(b) and the weaker the base

Question 39

Equilibrium Constant (K)

Answer 39

determines the extent of the reaction (whether it lies to the left or right side of the equation)

Question 40

strong vs weak acid/base

Answer 40

dissociates completely/ partially dissociates in aqueous solution

Question 41

Acid? Base? Conjugate Acid? Conjugate Base?

Answer 41

proton donor proton acceptor species formed when base accepts a proton species left when acid donates a proton

Question 42

What is equilibrium?

Answer 42

state in which chemical activities or concentrations of the reactants and products have no net change overt time