# Chem

posted by on .

Any help is appreciated!

Gold has a density of 19.3 g/cm3. Do you think you could carry 2.40 cubic ft (rhetorical--don't answer)? How many pounds does 2.40 cubic feet of gold weigh? [453.6 g = 1 lb, 2.54 cm = 1 in, and 1 ft = 12 in.]

7.42e-2

A scientific oven is programmed to change temperature from 51.4 ºF to 207.4 ºF in 1.50 minute(s). Express the rate of change in degrees Celsius per second.

-1.16

A bug is observed to travel 72 cm in 7.5 seconds. What is the bug's speed in miles per hour?

.21

Thank you!

• Chem - ,

a isn't even close. Show your work and I'll find the error.
b is close but I obtained 1.7 or thereabouts.
c. 0.214 is the factor for cm/sec to mph. You still must multiply by cm/sec which is 72/7.5.

• Chem - ,

thanks! all i did for a was change 2.4 by converting it in the manner they said, from feet to inches, inches to centimeters. same with 19.3. i changes it from grams to pounds.

• Chem - ,

something tells me you divided instead uf multiplying somewhere. In problems like this, be sure to keep track of the units, so you cancel out the ones you don't want.

As for you answer of .00742 lbs, even a cursory sanity check would give a clue that it's bogus. Gold is heavy. Could you lift a cubic foot of it? I doubt it. So, on to the calculations. You want to convert ft^3 to lbs, knowing the various equivalents.

2.4 ft^3 * 12^3 in^3/ft^3 * 2.54^3cm^3/in^3 * 19.3g/cm^3 * 1lb/453.6g = 2892 lbs

• Chem - ,

Great! Thank you!

• Chem - ,

Hey, no problem. It was a real epiphany for me when I took physics, when I found out that units could be canceled just like numeric factors.