Download CHEM121 Experiment 1C NAME

CHEM121
Exp.1FBL
Due:
NAME_______________________________ page 1/2
Part 1: Separating colors using chromatography paper.
Diagram:
Sketch↓
1. See diagram left. Tape a strip of
chromatography paper on a stirring rod. Cut the
paper so that it does not rest on the bottom of the
beaker. Draw an ink mark (line) on the paper with
a black vis a vis pen. Place the paper and rod
across the top of a150 ml beaker Add water to the
beaker to below the ink mark. Set aside for 15-20
minutes, as the water migrates on the paper strip.
Complete part 2. Sketch the chromatography
paper and colors in the indicated space.
2. ANSWER ON THE BACKOF THIS SHEET:
Ink reflects its color while absorbing all others.
Why do the colors together on the paper strip
produce a black ink.
Addition materials needed per laboratory:
Part 1: 20 strips of 2 X 10 cm chromatography paper , 5 water soluble, black, vis a vis pens, scissors
Part 2: 13 0-10.00 mL graduated pipettes with 0-10 visible graduations.
Significant Figures: A number with more significant figures is a more reliable number.
Always include one (but not more than one) doubtful digit when collecting data (shown below as “*”). The
last sig.fig. is the doubtful digit. Sometimes moving the decimal point helps in determining the sig.figs.
Example: 0.00317* and 317* have 3 sig.figs. EXCEPTION: Counting numbers, such as “3 students,” are
high quality and reliable numbers (infinite sig. figs.).
All non- zero digits and zeros between non-zero digits are sig. figs. (Example: 10304* has 5 sig.fig. )
Zeros right of a decimal point and sig.figs. are sig.figs. (Examples: 0.06100* has 4 sig.fig. 0.061* has 2
sig.fig.) Zeros left of sig.figs. are not sig.figs. unless they are between sig.figs. (Examples: (0.061* has 2
sig.fig. 2.0610* has 5 sig.fig.) Zeros right of sig.figs.but left of a decimal point may or may not be
sig.figs. Example 31700 may have 3, 4, or 5 sig.figs.
DIVISION: Count the sig.figs. in your work. Round–off your answer to the smallest number of sig.figs. in
your work. (Example: 5.138* km / 2.6* hr= 1.9761538 km/hr = 1.9*[761538 km/hr =
2.0* km/hr (7>5).) Multiplication is similar.
SUBTRACTION: Subtracting a doubtful digit anywhere in your work results in a doubtful digit. (Example:
5.138*g - 2.2*g = 2.9*[3*8*g = 2.9*g (3*<5).) Addition is similar.
Part : 2 10.0 mL pipette (graduated from 1.0-10.00 mL):
[prep: Make available: Pipettes and bulbs]
1. ________________ Mass an empty, clean, and dry 20mL beaker. Dry the beaker using toweling. Use
paper toweling to transport the beaker.
2.________________Obtain a 10 mL pipette and a 100 mL beaker 1/2 filled with deionized (not tap) water.
Use the rubber bulb to draw water into the pipette until the water level is above the 0.00 mark. Remove the
bulb and use your finger to adjust the water level until reading across the bottom of the meniscus (curved
water surface) is between 0.00 and 1.00 mL(eg. 0.17mL) Prevent further drainage. Do not round-off
collected data.
CHEM121
Exp.1FBL Due:
NAME_______________________________ page 2/2
3. ________________Allow the water in the pipette to drain in the 20 mL beaker (step #1) until the water
level reading is between 8.00 and 9.50 mL in the pipette . Read the final water volume to the nearest 0.01
mL (eg: 8.73 mL). Do not round-off collected data.
4._________________ Mass the beaker and water.
5.__________________ Calculate the pipette volume of the water (steps #2 and #3) using
v = vfinal - vinitial , the initial and final volumes on the pipette. Your answer should have at least 3 sig.fig.
6. __________________Calculate the mass of the water (steps #1 and #4) using: mw = m total – mbeaker
Your answer should have 4(or more) sig.fig.
7.__________________ Calculate the volume of the water using its mass( step #6). Use the density of
water. Circle the appropriate temperature and density (in g/mL with 4 sig.fig.) in the table below. Then use
the equation: v = mw / density (or mw ÷ density) to calculate the volume. Round-off your answer to at
least 4 sig.fig.
Temp. Density
18 oC 0.9986
Temp. Density
20 oC 0.9982
Temp. Density
22 oC 0.9978
Temp. Density
24 oC 0.9973
Temp. Density
26 oC 0.9968
8. Why is your answer to step #7 better (more reliable) than your answer in step #15? Answer below:
.