it\'s an online HW assignment, and my answer is apparently wrong(significant fig
ID: 1666185 • Letter: I
Question
it's an online HW assignment, and my answer is apparently wrong(significant figures are important here). maybe i'm having asemantics issue?anyway, i tried solving this using the surface area of a sphereformula --> S.A. = 4r^2, and came up with an answer of r =7e^-7 m. can anyone point me in the right direction? thanks.
question:
A typical adult human lung contains about 300 million tiny cavities called alveoli. Estimatethe average diameter of a single alveolus. Assume the alveoli arespherical and a typical human lung is about 2 liters.
Explanation / Answer
I'm not sure why you are using the surface area formula; you needthe formula for a sphere's volume. Let's back up a bit first,though: First convert 2 liters to cubic meters. There are 1000 litersin a cubic meter, so 2 / 1000 = 0.002 m3. Assuming the alveoli take up all the lung's volume, we divide 0.002by 300 million: 0.002 / (300 * 106) = 6.67*10-12m3 per alveoli. The volume of a sphere is equal to (4/3)r3. So we have: (4/3)r3 = 6.67*10-12 Now solve for r: r3 = 5.0*10-12 r3 = 1.59*10-12 r = 1.17*10-4 m diameter = 2*r = 2.34*10-4 m, or 0.234 millimeters That's what I get for the diameter. Now, the problemstatement has only 1 sig fig (lung is "2" liters), so if you wereto go by that, you would get 2*10-4 m. However, Idon't know your specific rules about how you treat your sigfigs.
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