Word problems from 8/25
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8. There are 7.11 x1024 molecules in 100.0 cm3 of a certain substance.
a. What is the number of molecules in 1.09 cm3 of the substance? 7.75 x 1022 molecules
b. What is the number of molecules in 2.24 x 104 cm3 of the substance? 1.59 x 10 27 molecules
c. What number of molecules would be in 9.01 x 10-6 cm3? 6.41 x 1017 molecules
9. The number of transistors on a particular integrated circuit board is 3 578 000, and the board
measures 9.5 mm x 8.2 mm.
a. What is the area occupied by each transistor? 2.2 x 10-5 mm2/transistor
b. Using your answer from (a), how many transistors could be formed on a silicon sheet that
measures 353 mm x 265 mm? 4.3 x 109 transistors
10. A solution has 0.501 g of a substance in 1.00 L. Express this concentration in grams per microliter (1 µL = 10-6 L).
5.01 x 10-8 g/µL
11. Cesium atoms are the largest of the naturally occurring elements. They have a diameter of 5.30 x 10 -10 m.
Calculate the number of cesium atoms that would have to be lined up to give a row of cesium atoms 2.54 cm long.
4.79 x 107 cesium atoms
12. The neutron has a volume of approximately 1.4 x 10 -44 m3 and a mass of 1.675 x 10-24 g.
Calculate the density of the neutron in g/m3. What is the mass of 1.0 cm3 of neutrons in kilograms?
1.2 x 1020g/m3; 1.2 x 1014 kg
13. The pits in a CD are some of the smallest things ever mass produced mechanically by humans. These pits represent
the 1s and 0s of digital information on a CD. These pits are only 1.6 x 10-8 m deep. How many of these pits would have to
be attacked on top of each other to make a hole 0.305 m deep? 1.9 x 107 pits
14. 22 400 mL of oxygen gas contains 6.022 x 1023 oxygen molecules at 0 οC and standard atmospheric pressure.
a. How many oxygen molecules are in 0.001 mL of gas? 2.69 x 1018 molecules of oxygen
b. How many oxygen molecules are in 1.00 L gas? 2.69 x 1022 molecules of oxygen
c. What is the average space in mL occupied by one oxygen molecule? 3.72 x 10-20 mL/ molecule
15. The mass of the atmosphere is calculated to be 5.136 x 1018 kg, and there are 6 500 000 000 people living on Earth.
Calculate the following values.
a. The mass of atmosphere in kg per person. 7.9 x 108 kg/person
b. The atmosphere in metric tons per person ( 1 metric ton = 1000 kg) 7.9 x 105 metric tons /person
c. If the number of people increases to 9 500 000 000, what is the mass in kg per person? 5.4 x 108 kg/person
16. The mass of the sun is 1.989 x 1030 kg, and the mass of Earth is 5.974 x 1024 kg. How many Earths would be needed
to equal the mass of the sun? 3.329 x 105 Earths
17. A new landfill has dimensions of 2.3 km x 1.4 km x 0.15 km.
a. What is the volume in km3? 4.8 x 10-1 km3
b. What is the volume in m3? 4.8 x 108 m3
c. If 250 000 000 objects averaging 0.060 m3 each are placed into the landfill each year, how many years will it
take to fill the landfill? 32 years
18. A dietary calorie (C ) is exactly equal to 1000 cal. If your daily intake of food gives you 2400 C, what is your intake in
joules (J) per day? (1 cal = 4.184 J) 1.0 x 107 J/day