Chapter 9 - Calculations Used in Analytical Chemistry

Question 1

It is a method to measure how much a chemical substance absorbs light

Answer 1

Spectrophotometry

Question 2

How does Spectrophotometry work?

Answer 2

It measure the intensity of light as the beam of light passes through sample solution

Question 3

Basic principle of Spectrophotometry

Answer 3

Each compound absorbs or transmits light over a certain range of wavelength

Question 4

Wavelength of visible light

Answer 4

~400 nm to ~700 nm

Question 5

It is an unchanging measure of the quantity of matter

Answer 5

Mass (m)

Question 6

It is the force of gravitational attraction between that matter and Earth

Answer 6

Weight (w)

Question 7

A ______ _____ is always based on _____ so that the results will not depend on ______

Answer 7

• chemical analysis
• mass
• locality

Question 8

It is a precision weights used to calibrate weighing instruments and ensure accurate measurements

Answer 8

Calibration Weights

Question 9

Calibration weights is used to

Answer 9

calibrate weighing instruments and ensure accurate measurements

Question 10

Four fundamental ways to express solution concentration

Answer 10

1. Molar concentration
2. Percent concentration
3. Solution-diluent volume ratio
4. p-functions

Question 11

It is the number of moles of that species that is contained in 1 L of the solution

Answer 11

Molar concentration (cx)

Question 12

Molar concentration (cx) formula

Answer 12

cx = nx/V
molar conc. = no. moles solute/volume of liters

Question 13

Unit of molar concentration

Answer 13

molar (M)

Question 14

Molar (M) dimensions

Answer 14

mol/L, or mol L ^ -1

Question 15

Molar concentration is also the number of

Answer 15

millimoles of solute per milliliter of solution

Question 16

Other way to express concentration

Answer 16

in terms of percent (parts per hundred)

Question 17

Three common methods to express percent concentration

Answer 17

1. weight percent (w/w) = weight solute/weight solution x 100%
2. volume percent (w/w) = volume solute/volume solution x 100%
3. weight/volume percent (w/v) = weight solute, g/volume solution, mL x 100%

Question 18

has the advantage of being temperature independent

Answer 18

weight percent

Question 19

For very ______ _____, ____ ___ ____ (ppm) is a convenient way to express concentration

Answer 19

• dilute solutions
• parts per million (ppm)
  Cppm = mass of solute/mass of solution x 10^6 ppm

Question 20

For even more dilute solutions, what is used to express concentration

Answer 20

perts per billion (ppb
Cppb = mass of solute/mass of solution x 10^9 ppb

Question 21

The composition of a dilute solution is sometimes specified in terms of the

Answer 21

volume of a more concentrated solution and the volume of solvent used in diluting it

Question 22

The volume of the former is separated from that of the latter by a _____

Answer 22

colon

Question 23

Scientists frequently express the concentration of a species in terms of its _____, or _____

Answer 23

p-function, or p-value

Question 24

It is the negative logarithm (to the base 10) of the molar concentration of that species

Answer 24

p-value

Question 25

p-value is expressed as

Answer 25

pX = -log [X]

Question 26

______ of a substance is its mass per unit volume (kg/L or g/mL)

Answer 26

Density

Question 27

units of density

Answer 27

- kg/L - g/mL

Question 28

It is the ratio of its mass to the mass of an equal volume of water at 4°C (dimensionless)

Answer 28

Specific gravity

Question 29

It is the quantitative relationship among the amounts of reacting chemical species

Answer 29

Stoichiometry