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Elements, as listed on the Periodic Table have atomic numbers, whereas molecules, like water (H2O) have molecular weight, which is the sum of all of the atomic masses of the atoms in a molecule. Each of the components of H2O have an atomic number: Hydrogen has an atomic number of 1 (because it has 1 proton); Oxygen has an atomic number of 8 (it has 8 protons). So, if a person were to try to assign an atomic 'number' to H2O they would likely come up with 2 x 1 (for the 2Hydrogens) + 8 (for the Oxygen) = 10! Now, because an atomic 'number' indicates an element on the periodic table, we'd have to look at the periodic table...and find that 10 is Ne (Neon). As you can see, this would be completely wrong as water is NOT neon! So, water does not have an atomic number. It does, however have a molecular weight! The molecular weight of H2O can be calculated by referring to the periodic table, where we would find that Hydrogen has a weight of 1.0079 grams per mol and Oxygen has an atomic weight of 15.9994 grams per mol. The molecular weight of H2O can be calculated by figuring out how many of each atom is in the molecule, and then multiplying each by it's weight. So: Hydrogen has an atomic weight of 1.0079 and there are two of them in H2O: 1.0079 x 2 = 2.0158 grams per mole Oxygen has an atomic weight of 15.9994 and there is one in H20: 15.9994 x 1 = 15.9994 grams per mole Add them up! 2.0158 + 15.9994 = 18.0152 grams per mole H20 has a molecular 'weight' of 18.152 grams!
Wiki User
∙ 16y ago
Wiki User
∙ 15y agowater is a compound so there is no atomic number for it. that is a trick question because only elements have an atomic number.
Wiki User
∙ 14y agoIf your talking about molar mass, the molar mass of H2O is 18g.mol-1
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∙ 8y agoWiki User
∙ 14y ago18.
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Why does the volume of the water vapor increase and the mass remain constant When 1 gram of water is evaporated?
Mass is mass. It is constant. Changing water from liquid to gas does not change the mass, it only changes the density, which is mass per volume. Look at it another way - in gaseous form, the same mass of water has the same number of molecules of water - but those molecules are simply further apart.
A molecule of water is composed of two atoms of hydrogen and one atom of oxygen if the atomic mass number of hydrogen is 1 and the molecular mass of water is 18 the atomic mass of oxygen must be?
16
How do you calculate the mass in grams of 6.073 molecoles of water?
You divide the 6.073 by 6.022x1023 (avagadros number) to get the moles, then multiply by molecular mass (18) to get mass in grams
How is the number of water of crystallization determined?
The number of water molecules in a hydrate can be determined by Thermogravimetric analysis. In a laboratory, it can be done as follows.Take a hydrated salt sample of known mass, m1.Heat it in the presence of a dessicant to dehydrate it, measure the mass again. Let this mass be m2.Subtract m2 from m1. This is the mass of water present in the sample, m.Divide the factor m with molar mass of water i.e. 18.015 g.The factor given thus is the number of water molecules in the sample.It should be kept in mind that this method is not as accurate as the termogravimetric analysis.Check the related links for more information.
What is the atomic number for ice?
ice is solid form of water so doesn't have atomic number its atomic mass will be 18
Does water have a mass of 18 grams?
It is water's molecular weight or mass number that equals 18 atomic mass units
When boiling water turns to steam what stays the same?
The mass of the water The number of molecules
What mass of water will contain 2.80 moles of water?
number of moles = Massdivided by Molar Mass 2.80 = Mass divided by 18.012.80 X 18.01 = MassMass = 50.43 grams.
Why does the volume of the water vapor increase and the mass remain constant When 1 gram of water is evaporated?
Mass is mass. It is constant. Changing water from liquid to gas does not change the mass, it only changes the density, which is mass per volume. Look at it another way - in gaseous form, the same mass of water has the same number of molecules of water - but those molecules are simply further apart.
How would you find out how much 12.4 moles of water weigh?
Multiply moles by molecular mass of water (18), gives you 223.8g. Remember this formula: Number of moles = mass / molecular mass
A molecule of water is composed of two atoms of hydrogen and one atom of oxygen if the atomic mass number of hydrogen is 1 and the molecular mass of water is 18 the atomic mass of oxygen must be?
16
How do you calculate the mass in grams of 6.073 molecoles of water?
You divide the 6.073 by 6.022x1023 (avagadros number) to get the moles, then multiply by molecular mass (18) to get mass in grams
What is the formula for a hydrate?
CALCULATING MASS OF WATER LOST IN HYDRATETo calculate how much water was lost after a hydrate's been heated, subtract the mass of the anhydrate (after) from the mass of the hydrate (before).Mass Hydrate - Mass Anhydrate = Mass Water LostEXPERIMENTAL VALUE PERCENT WATER IN HYDRATETo calculate the experimental percent of water in a hydrate (using values gathered during the experiment), calculate how much water was lost (see "CALCULATING MASS OF WATER LOST" above). Do this by dividing the mass of the water lost (g) by the mass of the hydrate. Multiply the result by 100%.mass water lost- mass hydrate x 100%THEORETICAL VALUE PERCENT WATER IN HYDRATETo calculate the theoretical percent of water in a hydrate (using molar masses of substances rather than actual masses from experimental data), divide the molar mass of the water molecules by the molar mass of the hydrate; multiply the result by 100%.- Molar mass waterMolar mass hydrate x 100%Finding Molar Mass# atoms element A * atomic mass element A = Mass A# atoms element B * atomic mass element B = Mass B... etc.Add up all the mass values and you have the molar mass. Do this for both the anhydrate and water. For water's molar mass, you can also multiply 18.02 by the number of water molecules there are. This is a useful number to remember in order to save time test day and while doing homework practice problems too.To find the molar mass of the hydrate, add the molar mass values for water and the anhydrate.Molar Mass Water Molecules + Molar Mass Anhydrate = Molar Mass HydratePERCENT ERROR WATER IN HYDRATEIn order to determine the percent error of the water in a hydrate, subtract the experimental value (what you determined using values found via experimentation) from the theoretical value (what is determined using molar masses), then divide value by the theoretical value; multiply result by 100%.Theoretical Value - Experimental Value x 100%----------- Theoretical ValueEMPIRICAL FORMULA OF HYDRATES(looking for quantity of water molecules)In order to find how many water molecules there are within a hydration (finding the empirical formula for hydrate), follow the steps below according to what is given.1. Calculate percent water in substance.Divide the mass of water by the mass of the hydrate (before heating).- mass water*mass hydrate* see "CALCULATING MASS OF WATER LOST IN HYDRATE" above. Sometimes this number is already given. If it is, then proceed to the next step.2. Convert Mass to Moles.Divide the mass of substance by its molar mass.--------- Mass substance (g)Molar mass substance (g/mol) = molConversion Factormass substance (g) x 1 mol substance----------------- atomic mass substance (g) = mol substanceDo this for both the anhydrate and water.3. Find Mole Ratio; Multiply the number of moles until they are a whole number.Find the mole ratio by dividing the number of moles for each substance by the smallest number of moles within the compound.------- # mol anhydratesmallest # moles compound--------- # mol watersmallest # moles compoundAND/OR-- mol H2Omol hydrate = mol H2O per mol anhydrateMultiply or are within
What is the theoretical percentage of water of hydration in cacl2-2h20?
1. Find the molar mass of the hydrate (Calcium Chloride Dihydrate).Find the molar mass of water and the anhydrate (anhydrate + water = hydrate); add the molar mass values of each to find the molar mass of the hydrate.Molar Mass CaCl2: 110.98g+ Molar Mass H2O: 36.04g*Molar Mass CaCl2 * 2H2O: 147.01gFinding Molar Mass# atoms element A * atomic mass element A = Mass A# atoms element B * atomic mass element B = Mass B... etc.Add up all the mass values and you have the value for molar mass. Do this for both the anhydrate and the water molecules. Add these values together to find the molar mass of the hydrate.Molar Mass Anhydrate + Molar Mass Water Molecules* = Molar Mass Hydrate* Tip: the molar mass of water for all hydrate calculations is 18.02g x number of water molecules. This number may be useful to remember on the day of the test or while doing practice problems.*2. Calculate the percentage of water in hydrate.Divide the molar mass of water by the molar mass of the hydrate, and multiply result by 100%.36.04g147.01g x 100%Percent water in hydrate is 24.52%.
How is the number of water of crystallization determined?
The number of water molecules in a hydrate can be determined by Thermogravimetric analysis. In a laboratory, it can be done as follows.Take a hydrated salt sample of known mass, m1.Heat it in the presence of a dessicant to dehydrate it, measure the mass again. Let this mass be m2.Subtract m2 from m1. This is the mass of water present in the sample, m.Divide the factor m with molar mass of water i.e. 18.015 g.The factor given thus is the number of water molecules in the sample.It should be kept in mind that this method is not as accurate as the termogravimetric analysis.Check the related links for more information.
What is the mass in grams of 3.41x10e26 molecules of water?
first you divide by avagadro's number to get the number of moles. 3.41x10^26 / 6.022x10^23 = 566.25 moles The molecular mass of water is 18. moles is mass/molecular weight so moles by the mass is the weight. 566.25*18 is 10192.63g. This is 10.193kg. Are you sure your molecule count was not exponentially lower?
What is the atomic number for ice?
ice is solid form of water so doesn't have atomic number its atomic mass will be 18
