The molecular mass of water molecule is 18g/mol. It implies that 1 mol of water molecules weigh18 g. 18 g of water contain 1 mol of watermolecules. or 18 g of water contain 6.022 x 10^23water molecules.
In summary, for a typical human of 70 kg, thereare almost 7*1027atoms (that's a 7 followed by27 zeros!) Another way of saying this is "seven billion billionbillion." Of this, almost 2/3 is hydrogen, 1/4 is oxygen, and about1/10 is carbon. These three atoms add up to 99% of thetotal!
Compounds contain two or more different elements.Water is a molecule because it containsmolecular bonds. Water is also a compound because itis made from more than one kind of element (oxygen and hydrogen).This type of molecule is called a diatomic molecule,a molecule made from two atoms of the sametype.
A mass in grams numerically equal to themolecular weight contains one mole of molecules,which is known to be 6.02 x 10^23 (Avogadro's number). So if youhave x grams of a substance, and the molecular weightis y, then the number of moles n = x/y and the number ofmolecules = n multiplied by Avogadro's number.
Water is wet, in the sense of being a liquidwhich flows easily, because its viscosity is low, which is becauseits molecules are rather loosely joined together.
Water (H2O) is made from 2 atoms ofhydrogen and 1 atom of oxygen. A mole of water moleculeswould be 2 moles of hydrogen atoms plus 1 mole ofoxygen atoms. Atomic mass is the number of grams per mole ofthe element. This means 1 mole of hydrogen weighs 1.0079grams and 1 mole of oxygen weighs 15.9994grams.
Hence, 1 gm water will = 1 mlwater. Since, 1 mol water = molecular mass in gm= 18gm.
| Density | Number of Water Molecules per cubic metric unit |
|---|
| Water | 1 gram/cm3 | 3.345 x 1022 molecules per cm3 |
| Rock | 2.67 gram/cm3 | 8.9 x 1022 molecules per cm3 |
| Earth | 5.5 gram/cm3 | 1.8 x 1023 molecules per cm3 |
| Sun | 1.4 gram/cm3 | 4.683 x 1022 molecules per cm3 |
For H2O, there is one atom of oxygen andtwo atoms of hydrogen. A molecule can be made of only onetype of atom. In its stable molecular form, oxygen exists astwo atoms and is written O2. to distinguish it from anatom of oxygen O, or ozone, a molecule of three oxygenatoms, O3.
So the number of molecules in a typical humancell is somewhere between 5 million and 2 trillion, probablycloser to the higher end of this range as human cells areroughly half water (85% of the human body is water, 60% of this isinside cells).
Chemists generally use the mole as the unit forthe number of atoms or molecules of a material. Onemole (abbreviated mol) is equal to6.022×1023 molecular entities (Avogadro's number),and each element has a different molar mass depending on the weightof 6.022×1023 of its atoms (1mole).
Mole— A Unit of Measurement
Like all units, a mole has to be based onsomething reproducible. A mole is the quantity of anythingthat has the same number of particles found in 12.000 grams ofcarbon-12. That number of particles is Avogadro's Number, which isroughly 6.02x1023.Multiply Moles by the Avogadro Constant
Multiply the number of moles by the Avogadro constant,6.022 x 10^23, to calculate the number of moleculesin your sample. In the example, the number of molecules ofNa2SO4 is 0.141 x 6.022 x 10^23, or 8.491 x 10^22 moleculesof Na2SO4.The water molecule is very simple. Amolecule is a piece of matter that contains two or moreatoms. It is called H2O because it has two atoms of hydrogen (H)and one atom of oxygen (O). There are millions of thesemolecules in one drop of water. The form watertakes depends on the movement of the watermolecules.
One sulfuric (H2SO4) molecule has 2 hydrogenatoms, 1 sulfur atom, and 4 oxygen atoms. You canalso say one mole of sulfuric acid has two mols of hydrogenatoms, 1 mol of sulfur atoms, and 4 moles of oxygenatoms. So in total, we have 7 mols of atoms. Butthat's in 1 mol of sulfuric acid.
A teaspoon of water (about 5 mL) contains2×1023water molecules, but each watermolecule is comprised of 3 atoms: two hydrogen and oneoxygen.
Water is made up of two hydrogen (H) atoms andone oxygen (O) atom. The formula for water isH2O. The hydrogen atoms have filled orbitals with twoelectrons and the oxygen atom is filled with eightelectrons.
There are 16 cups to the gallon, so multiplyinggallons of ocean water by 16 equals 5,642.72 quintillion or5.64272 sextillion cups. Keep in mind that the volume of theEarth's oceans is not static. The use of satellitesexpresses the surface area covered by oceans.
But the oceans are huge so you might thinkNapoleon's molecules would be spread out. Actually, theaverage distance between the molecules is small. Theoceans contain about 1.3 billion cubic kilometers ofwater (about 315 million cubic miles).
A molecular formula consists of the chemicalsymbols for the constituent elements followed by numeric subscriptsdescribing the number of atoms of each element present in themolecule. The empirical formula represents thesimplest whole-integer ratio of atoms in a compound.
- Quora. How many water molecules are present in18g of water? → there're about 6.023 x 10^23molecules in 18g of water !
A water molecule, because of its shape, isa polar molecule. That is, it has one sidethat is positively charged and one side that isnegatively charged. The molecule is made up of two hydrogenatoms and one oxygen atom. The bonds between the atoms arecalled covalent bonds, because the atoms shareelectrons.
The density of water is 1g/(cm3) so in1 gallon of water ( about 3.785 Liters or 3785cm3) the mass of the water is, 3785g. 1 mole of6.02x1023molecules of water is equal hasthe mass in grams equal to the molecular weight or 18 grams permole. so 3785 grams corresponds to about 1.265 x 1026molecules of water.
Avogadro tells us that we have 6.023 x 10^23 SiO2 unitsper gram, so there would be 6.023 x 10^23 / 60 ≈ 1 x 10^22SiO2 units in a gram of pure SiO2, and with SiO2 composed of 3atoms, that puts us at 3 x 10^22 atoms per gram ofSiO2. Now, a grain of sand does not weigh 1 gram. It weighsless.
There is an estimated 1.332 billion cubic kilometers ofsea on Earth and 0.05 ml of water in a drop,so the ocean is equivalent to 2.664 × 10^25 drops or26,640,000,000,000,000,000,000,000.
Once you know the molecular weight of a compound, youknow how much Avogadro's number of that compound weighs ingrams. To find the number of molecules in a sample,divide the weight of the sample by the weight of one mole to getthe number of moles, then multiply by Avogadro'snumber.
