MIDTERMS

Question 1

use to judge the quality of experimental measurements are many.

Answer 1

Statistical calculations

Question 2

Impossible:
Possible:

Answer 2

Impossible:
The analytical results are free of errors or uncertainties.
Possible:
Minimize these errors and estimate their size with acceptable accuracy.

Question 3

Chemists usually carry _____ of a sample through an entire analytical procedure

Answer 3

two to five portions (replicates)

Question 4

Mean, arithmetic mean, and average (X) are synonyms for the quantity obtained by dividing the sum of replicate measurements by the number of measurements in the set

Answer 4

Mean

Question 5

The _____ is the middle result when replicate data are arranged in order of size.

For an odd number of data points, the _____ can be evaluated directly.

For an even number, the _____ of the middle pair is used.

Answer 5

Median

Question 6

_____ describes the reproducibility of measurements; the closeness of results to each other.
* _____ is determined by repeating the measurement on replicate samples.
* Three terms to describe the ____ of a set of replicate data: standard deviation, variance, and coefficient of variation.

Answer 6

Precision

Question 7

Three terms to describe the precision of a set of replicate data: ______, _____, and _____.

Answer 7

standard deviation, variance, and coefficient of variation.

Question 8

_____ is the closeness of results to others that have been obtained in exactly the same way.

Answer 8

Precision

Question 9

_____ indicates the closeness of the measurement to its true or accepted value and is expressed by the error.

_____ measures agreement between a result and its true value.

Answer 9

Accuracy

Question 10

The _____ in the measurement of a quantity x₁

Answer 10

absolute error E

Question 11

is a more useful quantity than the absolute error.

is also expressed in parts per thousand (ppt).

Answer 11

Relative Error

Question 12

a finite number of experimental observations is called a _____

Answer 12

sample of data

Question 13

Statisticians call the theoretical infinite number of data a _____, more specifically a parent population, or a universe, of data.

Answer 13

population

Question 14

is a measure of the precision or scatter of a population of data

Answer 14

Population Standard Deviation (σ)

Question 15

Another term to describe the precision of a set of replicate results.

It is the difference between the largest value in the set and the smallest.

Answer 15

Spread or Range (w)

Question 16

is defined as the mass relationships among reacting chemical species.

Answer 16

Stoichiometry

Question 17

gives the simplest whole-number ratio of atoms in a chemical compound.

Answer 17

empirical formula

Question 18

specifies the number of atoms in a molecule.

Answer 18

molecular formula

Question 19

provides additional information.

Answer 19

structural formula

Question 20

is a statement of the combining ratios, or stoichiometry (in units of moles), among the reacting substances and their products.

Answer 20

balanced chemical equation

Question 21

This reactant limits the chemical reaction.

It is also called _______.

It is completely used up in the reaction, and thus determines when the reaction stops.

Answer 21

Limiting Reactant / limiting reagent

Question 22

Most of the solutes we discuss are ______, which form ions when dissolved in water (or certain other solvents) and thus produce solutions that conduct electricity.

Answer 22

electrolytes

Question 23

______ electrolytes ionize essentially completely.

Answer 23

strong

Question 24

____ electrolytes ionize only partially.

Answer 24

weak

Question 25

acid is a ______ and base is a
____

Answer 25

proton donor / proton acceptor

Question 26

Species produced when an acid gives up a proton is a potential proton acceptor called _____.

Answer 26

the conjugate base of the parent acid

Question 27

is the product that is different from a base by one proton. Whenever a base accepts a proton, an acid is formed.

Answer 27

Conjugate acid

Question 28

Some species have both acidic and basic properties and are called

Answer 28

amphiprotic solutes.

Question 29

behave as acids in the presence of basic solutes and bases in the presence of acidic solutes.

Answer 29

Amphiprotic solvents

Question 30

______ acids react with water so completely that no undissociated solute molecules remain.

Answer 30

STRONG

Question 31

The others are ____ acids, which react incompletely with water to give solutions that contain significant amounts of both the parent acid and its conjugate base

Answer 31

WEAK