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Water consists of hydrogen and oxygen, and the approximate

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Water consists of hydrogen and oxygen, and the approximate [#permalink] New post 18 Jan 2008, 11:33
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D
E

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58% (02:25) correct 42% (00:05) wrong based on 11 sessions
Water consists of hydrogen and oxygen, and the approximate ratio, by mass, of hydrogen to oxygen is 2:16. Approximately how many grams of oxygen are there in 144 grams of water?

(A)16
(B)72
(C)112
(D)128
(E)142



-thanx
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Re: water [#permalink] New post 18 Jan 2008, 11:36
portion of hydrogen in water is 2/(2+16) = 1/9.

weight of hydrogen = 144*1/9= 16.

A is the answer.
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Re: water [#permalink] New post 18 Jan 2008, 11:36
H and O are in a 1:8 ratio per gram of water

Therefore, in 144 gms of water, their ratio will be 16:128

Therefore, D.

vermatanya wrote:
Water consists of hydrogen and oxygen, and the approximate ratio, by mass, of hydrogen to oxygen is 2:16. Approximately how many grams of oxygen are there in 144 grams of water?

(A)16
(B)72
(C)112
(D)128
(E)142



-thanx
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Re: water [#permalink] New post 18 Jan 2008, 11:37
2x+16x=18x=144
x=8
8*16=128. D.
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Re: water [#permalink] New post 18 Jan 2008, 11:41
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

Answer D
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Re: water [#permalink] New post 18 Jan 2008, 11:43
eschn3am wrote:
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

Answer D





yeah thanx for explaining.
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Re: water [#permalink] New post 18 Jan 2008, 12:04
eschn3am wrote:
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

Answer D



hey but in the end y u multiplied it with the amount of oxygen instead of hydrogen :?:
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Re: water [#permalink] New post 18 Jan 2008, 12:23
oops, i calculated the amount of hydrogen, not oxygen. I should be more careful next time.
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Re: water [#permalink] New post 18 Jan 2008, 13:09
vermatanya wrote:
eschn3am wrote:
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

Answer D



hey but in the end y u multiplied it with the amount of oxygen instead of hydrogen :?:


The question is asking for the amount of oxygen. Always make sure you know exactly what the question is asking for before you answer it.
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Re: water [#permalink] New post 30 Oct 2010, 02:56
great thread .. i was getting 16 all the time .. just that i mixed up water and hydrogen
:))
Re: water   [#permalink] 30 Oct 2010, 02:56
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