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kmieciakp Teacher
High School - 12th GradePosted by kmieciakp on Saturday February 7, 2009 at 6:38 PMd=m/v
solve for m.
deterimine moles by dividing m by molecular weight (be sure to use same units).
determine molecules by mulitplying resulting moles by mole number (it's been awhile--I think it's 6.24 x 10 to the 23? called Avegerros' number? anyway, you can look it up.)
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sarahyama Teacher
Elementary / PrimaryPosted by sarahyama on Wednesday May 20, 2009 at 10:59 PMmromezy12,
To get the molecules, you should first solve how many grams of water are present. So you should multiply the density with the volume.
1.00g/ml times 2.56 ml is equal to 2.56g of water.
then multiply the mass with the molar mass of water. in water there are two hidrogen molecules and 1 oxygen molecule, so the molar mass would be 18.
Deviding 2.56g by 18g would give mole number of the water and to get the number of the molecules, you should times avogdro's number(6.23x10^23).
the answer would be 8.56x10^22
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neela Teacher
Graduate SchooleNotes Editor
Posted by neela on Monday June 8, 2009 at 10:34 PM18 gram of water contains 1 mole of water molecules.
The density of water at 4 deg C =1.00gm/mL.
Therefore, water by mass in 2.56 mL = =volume*density=2.56*1=2.56gm.
Number of water molecules in 1 gm of water=(1/18)mole=(6.022137 × 10^23 )/18molecules
Therefore the number of water molecules 2.56 gm of water:
=(2.56)(6.022137 × 1023)/18=8.564817067*10^22molecules of water.
