Chemistry Lab 124 - University of Dayton - Exam 1

Analytical Balance

5 sig figs or 4 if unstable and a line over the 4th digit

Thermometer

Three sig figs (20.5)

graduated cylinder (50mL)

3 Sig Figs (50.2)

Graduated Cylinder (10mL)

4 sig figs (10.25)

volumetric flask

5 sig figs

Buret

4 sig figs (27.22)

Pipet

4 sig figs (.02500L)

adding and subtracting sig figs

least number of decimal places added or subtracted

- 12.2 + 5.44 = 17.6

multiplying or dividing sig figs

the least number is the number of sig figs you can have in the answer

- 3.3 x 2.55 = 7.425

= 7.4

Qualitative Analysis

Identification of an unknown compound

precipitate

A solid that forms from a solution during a chemical reaction.

standard solution

the solution that contains the precisely known concentration of a solute

Supernatant

liquid remaining after the precipitate has settled

Preparation of a Volumetric Solution

1. Mass Compound on weigh dish

2. Transfer to a 100mL V.F.

- Rinse all compound into the flask w DI water

3. Add addition di water to fully dissolve the salt and get to the line

4. Transfer salt to a 250 mL beaker

5. Wash Flask and lid w soap and water

Titration

slowly adding one reactant to another, and measuring how much is needed for the subsequent reaction to be completed

Titrant

Base being slowly added

Analyte

Acid being analyzed

Stoichiometric/Equivalence point

When the analyte is completely neutralized

Endpoint

point at which the indicator changed colors

Indicator error

Difference between the endpoint ant equivalence point

standardization

analytical determination of the molarity of the solution

Primary Standard

a substance of very high purity which is stable in air

Precision

how close the results of the trials are to one another

Outliers

extreme values that don't appear to belong with the rest of the data

Accuracy

How close a experimentally determined value is

Calculation of molarity in a titration

1. mass/molar mass = moleKHP

2. mole (1mole/1mole) = moleNaOH

3. mole/vol NaOH L= molarity NaOH

Lattice Points

The points on a coordinate grid where the grid lines intersect.

Interstital site

Non-filled portion of the unitcell

coordination number

number of atoms or ions surrounding an atom or ion in a crystal lattice

Total Equivalent atoms

Cordination number of an interstitial site

number of atoms immediately surrounding it

Primitive Cubic Model

8 atoms

1/8 fraction

1 total equivalent atom

Coord Num = 6

body centered cubic

2 total equivalent atoms

8 coordination num

face centered cubic

12 coordination number

4 total equivalent atoms

4 atoms surround the interstitial site

Coordination number of the site is 6

Tetrahedral site

4 coord num