LAB EQUIPMENT & TECHNIQUES – btalance & burete
Objective:
To become familiar with common measuring instruments in the Chemistry laboratory. To handle calculations using significant figures appropriately. To demonstrate the density of water.
Procedure:
1. Obtain a triple beam balance. Zero it.
2. Obtain a burette; check to see that it flows freely; fill it with distilled water.
3. Obtain a medium-sized beaker (250 mL, 150 mL or 100 mL). Find its mass.
4. Set the burette so that the initial volume reading is 0.00 mL.
5. Withdraw water until approximately 10 mL of water is removed from the burette into the massed beaker.
6. Record the final volume reading on the burette.
7. Find the mass of the beaker and the added water. Record the mass.
8. Repeat steps 5,6 and 7 until the burette’s final reading is 50.00 mL (or close!). You should have 10 burette readings and six mass measures.
9. Repeat steps 2 through 8 but using methanol or ethanol.
10. Clean up your lab station and lock it!
DATA:
| OBJECT | Mass, g | Volume, initial, mL | Volume, final, mL |
| Beaker, empty | |||
| Beaker & ~10 mL water | |||
| Beaker & 20 mL water | |||
| Beaker & 30 mL water | |||
| Beaker & 40 mL water | |||
| Beaker & 50 mL water |
Results:
Water trial |
Mass,g | Volume, mL(total) | M/V |
#1 |
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#2 |
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#3 |
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#4 |
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#5 |
Graph the calculated mass vs. the calculated volume for each determination.
Questions:
1. To how many significant figures was each of your mass measures?
2. To how many significant figures was each of your volume measures?
3. What is the significance of the slope of the line that you graphed?
4. What would change if alcohol or carbon tetrachloride or mercury were used in this experiment. Be specific.
5. To how many significant figures can you report the ratios that you calculated?
HW: Read about significant figures in text. DO THIS BEFORE YOU ANSWER THE LAB QUESTIONS!
(pgs. 47-51; follow rounding rules 1 and 2 ONLY – disregard the rest!)
WRITE Lab Report! (Memorize symbols)