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# how much sand in a desert watch

1. the sahara desert is the largest desert in the world and is situated in the north of Africa. It stretches from the Atlantic Ocean to the Red Sea and finally ends near Iraq. It measures approximately 5000km east to west, and 2000km from North to South.
Assuming that each grain of sand is cubic, each side is 0.5mm in length and that the sand depth is 10 feet. calculate the number of 'moles' (avogadros number) of sand grains in the sahara desert.
anyone good at maths? lol
2. Isn't the Antarctic the biggest desert in the world.

Area of Sand = 5000000 x 2000000 square m
Volume of sand = 1.0x10^13 x (10/3) m (3ft aprox = 1m)
= 3.33'x10^13 cubic m

number of moles = mass of substance/Molar mass
sand is SiO2, which has a molar mass of 60.0843 g/mol
mass = density x volume, density of sand is 2.634 g/cm3
mass = 3.33x10^16(cubic cm) x 2.634 = 8.78x10^14 grams
moles = 8.78x10^14 / 60.0843

1.46x10^15 moles of sand in the sahara desert...... I think... does that seem right? I haven't done calculations with chemistry for a while, quite a lot of unit conversions here. Double check, I may have overlooked something.
3. according to our teacher, no. lol. she seems to think the sahara is...
ta 4 help.
4. A quick google define yeilded "the world's largest desert (3,500,000 square miles) in northern Africa".

5. Are you asking for help ? .... or testing our mathematical ability ?
6. (Original post by kerry3788)
according to our teacher, no. lol. she seems to think the sahara is...
ta 4 help.
The Sahara is the largest hot desert (9 million square kilometres). Antarctica is a desert, though, and is much bigger at 14 million square kilometres.
7. Are you lot serious.

'Maybe after this week can see how much water there is in the ocean, or how much mud there is in the uk'.
8. good idea, thats the next question, water!!
9. (Original post by alieg)
Isn't the Antarctic the biggest desert in the world.

Area of Sand = 5000000 x 2000000 square m
Volume of sand = 1.0x10^13 x (10/3) m (3ft aprox = 1m)
= 3.33'x10^13 cubic m

number of moles = mass of substance/Molar mass
sand is SiO2, which has a molar mass of 60.0843 g/mol
mass = density x volume, density of sand is 2.634 g/cm3
mass = 3.33x10^16(cubic cm) x 2.634 = 8.78x10^14 grams
moles = 8.78x10^14 / 60.0843

1.46x10^15 moles of sand in the sahara desert...... I think... does that seem right? I haven't done calculations with chemistry for a while, quite a lot of unit conversions here. Double check, I may have overlooked something.

thanks 4 helpin, i get confused with maths.... lol
10. I'm guessing it's over 9000.

Sorry.
11. As has been said, the Antarctic is the words largest desert by definition.

It is scentifically false to say the sahara is the largest desert in the world, it is not.
12. (Original post by alieg)
Isn't the Antarctic the biggest desert in the world.
no sand there though...
13. (Original post by Pocket Calculator)
no sand there though...
By definition a desert doesn't need sand.
14. bearing in mind a teacher set the question, the question is based on sand, and she says that the sahara is the biggest desert. for that particular question, a sand question, i think it would be a relevant assumption?!
15. Maybe she was trying to trick them eh
16. I would imagine there is a lot of sand.
17. (Original post by alieg)
Isn't the Antarctic the biggest desert in the world.
Ok then, kindly compare the amount of sand in the Antarctic to that of the Sahara
18. Anyone remember Squand?
19. (Original post by kerry3788)
the sahara desert is the largest desert in the world and is situated in the north of Africa. It stretches from the Atlantic Ocean to the Red Sea and finally ends near Iraq. It measures approximately 5000km east to west, and 2000km from North to South.
Assuming that each grain of sand is cubic, each side is 0.5mm in length and that the sand depth is 10 feet. calculate the number of 'moles' (avogadros number) of sand grains in the sahara desert.
anyone good at maths? lol

(Original post by alieg)
Isn't the Antarctic the biggest desert in the world.

Area of Sand = 5000000 x 2000000 square m
Volume of sand = 1.0x10^13 x (10/3) m (3ft aprox = 1m)
= 3.33'x10^13 cubic m

number of moles = mass of substance/Molar mass
sand is SiO2, which has a molar mass of 60.0843 g/mol
mass = density x volume, density of sand is 2.634 g/cm3
mass = 3.33x10^16(cubic cm) x 2.634 = 8.78x10^14 grams
moles = 8.78x10^14 / 60.0843

1.46x10^15 moles of sand in the sahara desert...... I think... does that seem right? I haven't done calculations with chemistry for a while, quite a lot of unit conversions here. Double check, I may have overlooked something.

The density or chemical composition of sand has nothing to do with it. All the OP needs basically is the number of sand grains, expressed in moles (which is just a unit really - you can have moles of anything, remember).

Total volume of sand
= 3.3 * 10^13 m3
= 3.3 * 10^22 mm3

each grain is 1/8 of a mm3 (0.5mm side length - would take 8 such blocks to make a cube of 1mm side length)

so, the above figure * 8 = 2.64 * 10^23

or we could say that here our units are not mm3 but 0.5mm3, see?

So there are 2.64 * 10^23 grains of sand there.

1 mole = roughly 6 * 10^23

wow, look, we're already at the same order of magnitude! What a coincidence.

2.64/6.02= 0.44 moles of sand-grains in that desert.

[EDIT: fail etc.]
20. oo - whos got the right answer, then, its close? i duno th answer, thats why i asked 4 help. lol

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