Unit 2 HomeworkPage 1 of 8
Name ____KEY______Period ____
CRHS Academic Chemistry
UNIT 2 - Measurement and Calculations
Homework
Due Date Assignment On-Time (100) Late (70)
______2.1
______2.2
______2.3
______2.4
______Warm Ups
Notes, Homework,Exam Reviews and Their KEYS located on CRHS Academic Chemistry Website:
WARM-UPS
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HW 2.1 CONVERSIONS FACTORS, DIMENSIONAL ANALYSIS, AND UNITS OF MEASURE
Convert the following metric measurements to the unit specified. (SHOW UNITS)
Problem / Calculation / Answer500 g = mg / / 500,000 mg
0.03 L = mL / / 30 mL
344 mg = _kg / / 0.000344 kg
0.004 cm = m / / 0.00004 m
4 cm =mm / / 40 mm
318 kg = mg / / 318,000,000 mg
0.12 mm= cm / / 0.012 cm
92 m =km / = / 0.092 km
105 mL =L / / 0.105 L
2674 cm = km / / 0.002674 km
Additional Dimensional Analysis Problems (SHOW UNITS)
11. The density of lead is 11.3 g/mL. What is the mass of 45 mL of the metal in grams?
12. What is the mass in kg of 11.0 mL of water that has a density of 1.00 g/mL?
13. A solution of barium nitrate contains 61.2 g per liter of solution (i.e. 61.2 g = 1 L). How many grams of barium nitrate is contained in 2.75 L of this solution?
14. A sample of seawater contains 6.277 g of sodium chloride per liter of solution (i.e. 6.277 g = 1L). How many mg of sodium chloride would be contained in 15.0 mL of this solution? (Hint – convert mL to L and then L to g and then g to mg).
HW 2.2 SIGNIFICANT FIGURES
Determine the number of significant figures in the each measurement
0.00040230 g5
405000 kg3
508.0 L4
0.049450 s5
820400.0 L7
0.000482 mL3
1.0200 kg5
Complete the following addition and subtraction problems, making sure that your answer contains the correct number of sig figs and show units.
258.3 kg + 257.11 kg + 253 kg= 768.41 kg = 768 kg
5.236 cm - 3.14 cm= 2.06 cm = 2.30 cm
0.0487 mg + 0.05834 mg + 0.00483 mg= 0.1119 mg = 0.112 mg
Complete the following multiplication and division problems, making sure that your answer contains the correct number of sig figs.
24 m x 3.26 m= 78.24 m = 78 m
4.84 m 2.4 s= 2.016 s = 2.01 s
120 m x 0.10 m= 12 m
102.4 m 51.2 s= 5242.88 s = 5240 s
1.23 m x 2.0 m= 2.46 m = 2.5 m
Solve: 3.20 cm x 3.65 cm + 21 cm 2= 11.68 cm2 + 21 cm2 = 32.68 cm2 = 33 cm2
HW 2.3 SCIENTIFIC NOTATION
Express the following quantities in scientific notation: ***Don’t Forget Your Units!***
700 m7x102 m
0.0054 kg5.4x10-3 kg
360,000 s3.6x105 s
0.000687 kg6.87x10-4 kg
38,000 m3.8x104 m
0.000000076 kg 7.6x10-8 kg
685,000,000 m 6.85x108 m
4,500,000 m4.5x106 m
Express the following quantities in ordinary notation:
8.348 x 106 km8,348,000 km
3.402 x 103 g3,402 g
7.6352 x 10-3 kg 0.0076352 kg
3.02 x 10-5 s0.0000302 s
3.1587 x 10-8 g0.000000031587 g
1.0200 x 105 kg102,000 kg
4.38 x 104 mm43,800 mm
5.72 x 10-4 cm0.000572 cm
One mole of copper contains 6.02 X 1023 atoms.(This is the equality & conversion factor!) How many atoms are there in 0.525 moles?
A mole of sodium atoms contains 6.02 X 1023 atoms. How many moles would be needed in order to have 25.0 X 1023 atoms?
A mole of hydrogen atoms contains 6.02 X 1023 atoms. A section of outer space contains 25 atoms. How many moles of hydrogen is this?
HW 2.4 ACCURACY AND PRECISION AND QUALITATIVE VS. QUANTITATIVE
Consider the following measurements in the table below. The values were recorded during a lab investigation in which the final mass value of the sample created should have been 26.30 grams.
Student / Trial 1 / Trial 2 / Trial 3Megan / 26.30 g / 26.29 g / 26.30g
Heather / 38.12 g / 26.30g / 12.43 g
Luis / 36.39 g / 36.40 g / 36.40 g
Adam / 24 g / 24 g / 24 g
George / 26.28g / 26.31 g / 26.32g
List the students’ names whose measurements were:
1)accurate AND preciseMeagan, George
2)precise but NOT accurateLuis
3)NEITHER precise NOR accurateAdam
4)accurate but not preciseHeather
5)Jake massed a known 200.0-g object and obtained a value of 253.3 grams. He repeated his measurement technique two additional times, obtaining values of 253.8 g and 252.9 g. Were his measurements ACCURATE, PRECISE, both or neither?
Answer and Explain Not Accurate (200.0 g actual vs. 253 measured) , but Precise (253 with 0.1 doubtful digit)
Use X’s for data points and draw examples of each description.
Label the following data as either qualitative or quantitative
15.6 cmquant
1.8 g/mLquant
slipperyqual
50.0 g_quant
bluequal
rotten odorqual
760nmquant
roughqual
Shortqual
Heavy qual
The cup had a mass of 454 grams. quant
The temperature outside is 250 C. quant
It is warm outside. qual
The tree is 30 feet tall. quant
The building has 25 stories. qual
The building is taller than the tree. qual
The sidewalk is long. qual
The sidewalk is 100 meters long. quant
The race was over quickly. qual
The race was over in 10 minutes. quant
The solution had a bitter taste.qual
The litmus paper turned red. qual