CHEM 121L Lab Final Exam

Question 1

Filtration

Answer 1

The separation of a liquid from a solid by particle size through a porous medium (i.e. filter paper).

Question 2

Residue

Answer 2

The solid left on the filter paper in filtration.

Question 3

Filtrate

Answer 3

The liquid that passes through the filter paper in filtration.

Question 4

Decantation

Answer 4

The separation of a liquid from a solid by pouring. The solid is allowed to settle to the bottom of its container, and the supernatant liquid is poured off, leaving the solid behind in the original container.

Question 5

Supernatant Liquid

Answer 5

A clear liquid free of precipitate that forms during the chemical process of precipitation and is located above the solid part during settling.

Question 6

Evaporation

Answer 6

The process used to separate a solvent from a solution by heating. The solvent is driven from the solution, leaving behind the previously dissolved residue.

Question 7

Extraction

Answer 7

The process used to isolate or purify a substance. This process selectively removes a compound of interest from a mixture based on its soul ability in a particular solvent. Once a desired compound has been extracted, the solvent can be removed through evaporation.

Question 8

% Composition

Answer 8

% = mass of component/mass of sample x 100

Question 9

Quantitative Analysis

Answer 9

Determines how much of a compound is present in a sample.

Question 10

Gravimetric Determination

Answer 10

The chemical compound of interest, the analyte, is precipitated as an insolvable compound and weighed.

Question 11

Volumetric Determination

Answer 11

The amount of analyte is determined by measurements of solution volumes that react with the analyte.

Question 12

Accuracy

Answer 12

A measure of how close a measurement is to the correct or accepted value of the quantity being measured.

Question 13

Precision

Answer 13

A measure of how close a series of measurements are to one another.

Question 14

Average Deviation

Answer 14

X = Sigma E Xi / n (all values added together and divided by the amount of values)

Question 15

Standard Deviation

Answer 15

A measure associated with the uncertainty of the laboratory procedure.

s = sqrt (sigma E (Xi - X)^2/n-1)), X is the average, Xi are the individual measurements

Question 16

Limiting Reagents

Answer 16

Substances that are completely consumed in the completion of a chemical reaction. Thus, this reagent limits how much product can be formed.

Question 17

Empirical Formula

Answer 17

Divide given moles by the smallest mole. Round answers to the nearest coefficient. This answers are your subscripts in the empirical formula.

Question 18

Molecular Formula from Empirical Formula

Answer 18

1. Determine molar mass of the empirical formula
2. Divide the given molecular molar mass by the molar mass calculated for the empirical formula
3. Multiply each subscript by the whole number that resulted from step 2

Question 19

Ionic Compounds

Answer 19

Compounds formed by the transfer of electrons between metals and non-metals.

Question 20

Metathesis Reactions (General Form)

Answer 20

An aqueous chemical reaction in which the cations and anions of the reactants change partners.

AX + BY —> AY + BX

Question 21

Molecular Equations

Answer 21

Balanced Equations

Question 22

Complete Ionic Equation

Answer 22

An ionic equation that shows all of the ions in the solution, regardless of whether they participate in the chemical reaction.

Question 23

Net Ionic Equation

Answer 23

An equation that shows only the ions that are involved in a reaction.

Question 24

Combination Reaction

Answer 24

Two elements or species come together to form one compound.

A + B —> AB

Question 25

Decomposition Reaction

Answer 25

One species decomposes into two or more chemical species, generally as a result of heating.

AD —> AB + C

Question 26

Single Displacement Reaction

Answer 26

One element displaces an atom in a compound to form a new compound while the displaced atom is converted to its elemental form.

AC + B —> A + BC

Question 27

Metathesis (Double Displacement Reaction)

Answer 27

The cation of the second species displaces the cation of the first species to form two new compounds. The two cations are exchanged.

AX + BY —> AY + BX

Question 28

Oxidation-Reduction Reaction

Answer 28

Two half reactions are added together.

A —> A(n+) + n e-
B + m e —> Bm-

A + B —> A(n+) + B(m-)

Question 29

Theoretical Yield

Answer 29

The amount of product you will get if all of the reactant reacts.
1. Balance the molecular equation
2. Identify the limiting reagent
3. Convert grams of limiting reactant to moles
4. Use the mole ratio between the limiting reactant and product to find the number of moles of product.
5. Convert moles of product to grams.

Question 30

Percent Yield

Answer 30

% Yield = actual yield / theoretical yield x 100%

Question 31

Titration technique

Answer 31

A method where a solution of a known concentration is used to determine the unknown concentration of a second solution.

Question 32

Titrant

Answer 32

the known solution in a titration. The solution found in the buret.

Question 33

Standardization

Answer 33

The process of determining the exact concentration (molarity) of a solution.

Question 34

Acid-Base Indicator

Answer 34

A solution that changes color depending on the pH (or acid content) of the solution

Question 35

End Point

Answer 35

The point in a titration that signifies the completion of the titration by a change in color of the solution.

Question 36

Equivalence Point

Answer 36

A point in a titration when the analyte has completely reacted with the titrant.

Question 37

Molarity

Answer 37

The number of moles of a solute dissolved in a liter of a solution.

Question 38

Molar Concentration

Answer 38

Molar Concentration (M) = moles of solute (n) / liters of solution (v)

Question 39

Effects of Ionic Compounds on Polymers

Answer 39

Ions from ionic compounds can interfere with the stability of the polymer-water interactions in the gel. Breaks down the gel and would act as an electrolyte.

Question 40

Effects of Molecular Compounds on Polymers

Answer 40

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Question 41

Trends in Atomic Radii

Answer 41

Increases down a column, increases left to right across a period