'A single molecule of H2O' vs 'a single atom of H2O'

[Indranil]

Which one is correct below
1. a single molecule of H2O
2. a single atom of H2O (if this one is correct then what does it mean?)

 

[Ilya Furman]

Which one is correct below
1. a single molecule of H2O
2. a single atom of H2O (if this one is correct then what does it mean?)

1. would be correct because H2O (water) is a MOLECULE which is composed of 2 Hydrogen ATOMS and 1 Oxygen ATOM.

 

[Indranil]

1. would be correct because H2O (water) is a MOLECULE which is composed of 2 Hydrogen ATOMS and 1 Oxygen ATOM.

Is 'a molecule of H2O' is the same as 'a single molecule of H2O'?

 

[Ilya Furman]

Is 'a molecule of H2O' is the same as 'a single molecule of H2O'?

Correct!

 

[Indranil]

Correct!

Then what is the mass of 1 H2O molecule?

 

[russ_watters]

Then what is the mass of 1 H2O molecule?

You tell us. that is an easy question that you should be able to answer by now. And show your work.

 

[russ_watters]

Mod note for other users: we are spoonfeeding this member too much. Please allow/demand s/he try to answer these questions hi/erself.

 

[Indranil]

You tell us. that is an easy question that you should be able to answer by now. And show your work.

OK,

Mod note for other users: we are spoonfeeding this member too much. Please allow/demand s/he try to answer these questions hi/erself.

Because in a site, I found two different masses of 1 molecule of H2O
one is 18.02 grams and the another is 2.992 x 10-23 grams that's why I am confused which one should I take? because as mentioned above, 'a molecule of H2O' and 'a single molecule of H2O' are the same thing. Then why are the different masses for ''1 molecule of H2O''
Source:https://www.thoughtco.com/avogadros-number-example-chemistry-problem-609541

 

[physics loverq]

OK,

Because in a site, I found two different masses of 1 molecule of H2O
one is 18.02 grams and the another is 2.992 x 10-23 grams that's why I am confused which one should I take? because as mentioned above, 'a molecule of H2O' and 'a single molecule of H2O' are the same thing. Then why are the different masses for ''1 molecule of H2O''
Source:https://www.thoughtco.com/avogadros-number-example-chemistry-problem-609541

okay...my last hint: check the units of the two values.

 

[russ_watters]

OK,

Because in a site, I found two different masses of 1 molecule of H2O
one is 18.02 grams and the another is 2.992 x 10-23 grams that's why I am confused which one should I take?

You just googled the answer. I want you to CALCULATE the answer. And show your work.

 

[Mark44]

Mod note for other users: we are spoonfeeding this member too much. Please allow/demand s/he try to answer these questions hi/erself.

For example, in post #2

1. would be correct because H2O (water) is a MOLECULE which is composed of 2 Hydrogen ATOMS and 1 Oxygen ATOM.

Our policy here is to NOT merely provide answers to posted questions.

 

[Asymptotic]

OK,

Because in a site, I found two different masses of 1 molecule of H2O
one is 18.02 grams and the another is 2.992 x 10-23 grams that's why I am confused which one should I take? because as mentioned above, 'a molecule of H2O' and 'a single molecule of H2O' are the same thing. Then why are the different masses for ''1 molecule of H2O''
Source:https://www.thoughtco.com/avogadros-number-example-chemistry-problem-609541

18.02 grams as the mass of a water molecule snapped my head around - a US penny coin is 2.5 grams!. You may wish to read up on molar mass, what it is, and how it is calculated.

 

[Ilya Furman]

For example, in post #2
Our policy here is to NOT merely provide answers to posted questions.

I was not aware of the procedure. I just joined today. I simply explained the difference between the two possible answers.

 

[Indranil]

okay...my last hint: check the units of the two values.

Mass of 1 H2O molecule is below
the first one is 18g/mol and the second one is 2.992 x 10-23 grams. Now I got it
The mass of 1H2O molecule in gram/mole unit
If I split 1 H2O molecule, we get 2H atoms and 1O atom
Mass of 1H atom is 1.01 g/mol and mass of 1O atom is 16g/mol so, the mass of 1H2O molecule is 18.02 g/mol------------------------------------ (1)
The mass of 1H2O molecule in gram unit
1H2O molecule = 18g/mol and 1H2O molecule = 6.023 X 10^23 molecules/mol
so 1H2O molecule = 18g/mol / 6.023 X10^23 molecules/mol = 2.992 x 10-23 grams
mass of 1 water molecule = 2.992 x 10-23 grams --------------------------------------------------------------------------------------------------------------------(2)
Please point out above where I am wrong.Thanking you

 

[HAYAO]

The answer is 99.9% correct. Well done.

To be a bit nitpicky, you calculated molecular weight of H₂O as 18.02 g⋅mol^-1 and not 18 g⋅mol^-1 so you should write it as so in your equations (calculating as 18 g⋅mol^-1 gives you 2.989x10^-23 g). That is the remaining 0.1% that you were wrong. You should make this a habit so that you won't mess up the significant figures as well.

 

[symbolipoint]

Which one is correct below
1. a single molecule of H2O
2. a single atom of H2O (if this one is correct then what does it mean?)

Big conceptual distinction. Molecule of water, YES. Single Atom of water, NO.

One mole of H₂O is made of 2 moles Hydrogen and 1 mole Oxygen. Thinking down to the finest units, 2 atoms of Hydrogen and 1 atom of Oxygen would make for 1 molecule of water, not accounting for isotopes.

 

[DrDu]

The mass of 1H2O molecule in gram/mole unit

This is not the molecular mass but the molar mass, i.e. the mass of one mole of H2O molecules.
Conceptually, a mole falls in the same category as "a dozen" or "a score".
A dozen of eggs has a higher mass than a single egg. In the same way, the mass of a mole of water molecules is much higher than the mass of a single water molecule.

 

[Borek]

The mass of 1H2O molecule in gram/mole unit

No, you can't express mas of a molecule in g/mol. g/mol is for molar mass, mass of a single molecule is just in grams (kilograms, or any other mass unit).

 

[russ_watters]

Please point out above where I am wrong.Thanking you

The answer is 99.9% correct. Well done.

Great job, @Indranil!

 

[Indranil]

Great job, @Indranil!

Thank you sir.

 

[Indranil]

No, you can't express mas of a molecule in g/mol. g/mol is for molar mass, mass of a single molecule is just in grams (kilograms, or any other mass unit).

Let me clear my concept
1. 'O + H2 = H2O', Here do one O atom and one H2 molecule (two H atoms) and one H2O molecule express molar mass? 1O = 16g/mole, 1H2 = 2g/mole and 1H2O = 18g/mole?
2.'C + O2 = CO2' Here one C atom and one O2 molecule (two O atoms) and one CO2 molecule express molar mass? 1C = 12g/mole, 1O2 = 32g/mole and 1CO2 = 44g/mole
So what elements we see in the periodic table and elements we use in making chemical equations, are in the form of ''molar mass'' or ''gram/mole''?
Please help me clear this concept. Thanking you.

 

[Drakkith]

1. 'O + H2 = H2O', Here do one O atom and one H2 molecule (two H atoms) and one H2O molecule express molar mass? 1O = 16g/mole, 1H2 = 2g/mole and 1H2O = 18g/mole?

What do you mean by 'express molar mass'? Each atom and molecule have a specific mass, which we commonly give in grams per mole of the substance. Molar mass is not a property that is 'expressed'.

So what elements we see in the periodic table and elements we use in making chemical equations, are in the form of ''gram/mole''?

All the elements have a molar mass. This is because molar mass is just the amount of mass per mole of the substance. It's like giving the mass of eggs as grams per dozen eggs. It's used because it is convenient for us.

 

[HAYAO]

Please help me understand this correctly:

1. "O + H₂ → H₂O", Here, are one O atom, one H₂ molecule (two H atoms), and one H₂O molecule expressed in molar mass units? That is, 1O = 16 g⋅mol^-1, 1H₂ = 2 g⋅mol^-1, and 1H₂O = 18 g⋅mol^-1?

2. "C + O₂ → CO₂" Here, are one C atom, one O₂ molecule (two O atoms), and one CO₂ molecule express molar mass? That is, 1C = 12 g⋅mol^-1, 1O₂ = 32 g⋅mol^-1, and 1CO₂ = 44 g⋅mol^-1?

What elemental symbol we see in the periodic table and in chemical reaction equations are in the form of ''molar mass'' or ''gram/mole'' units?
Thank you.

Proofread for clarity.Forget about the elements for now. Let's say we have some random stuff named A and another random but a different stuff named B. Combining one A and two B will give us one C:

A + 2B → C​

The reaction equation simply states that combining one A with two Bs will give you one C. Nothing more and nothing less. Same thing with elements. The elemental symbols itself are merely symbols to represent what element we are looking at.The numbers on the elements simply represent the ratio of each species in a reaction. They are certainly not in the units of molar mass. There are no units.

 

[symbolipoint]

Let me clear my concept
1. 'O + H2 = H2O', Here do one O atom and one H2 molecule (two H atoms) and one H2O molecule express molar mass? 1O = 16g/mole, 1H2 = 2g/mole and 1H2O = 18g/mole?
2.'C + O2 = CO2' Here one C atom and one O2 molecule (two O atoms) and one CO2 molecule express molar mass? 1C = 12g/mole, 1O2 = 32g/mole and 1CO2 = 44g/mole
So what elements we see in the periodic table and elements we use in making chemical equations, are in the form of ''molar mass'' or ''gram/mole''?
Please help me clear this concept. Thanking you.

Not the way you are saying.

(1)
One oxygen is bonded to TWO hydrogens. Separate bond for each.

(2)
One carbon is bonded to TWO oxygens. Separate bond for each.

 

[DrDu]

Proofread for clarity.Forget about the elements for now. Let's say we have some random stuff named A and another random but a different stuff named B. Combining one A and two B will give us one C:

A + 2B → C​

The reaction equation simply states that combining one A with two Bs will give you one C. Nothing more and nothing less. Same thing with elements. The elemental symbols itself are merely symbols to represent what element we are looking at.The numbers on the elements simply represent the ratio of each species in a reaction. They are certainly not in the units of molar mass. There are no units.

I can only agree strongly. Formulas like $\mathrm{H_2O}$ were written long before it was known or widely accepted, that matter is made up of molecules and atoms. Even today when working in preparative chemistry, you can live well without even knowing about Avogadro's constant.

 

[Indranil]

Not the way you are saying.

(1)
One oxygen is bonded to TWO hydrogens. Separate bond for each.

(2)
One carbon is bonded to TWO oxygens. Separate bond for each.

This is not my question. My question is simple. What should I say from the equations below?
1. H2 + O = H2O
My first question is
What should I say from this equation? I think we say one H2 molecule(two H atoms) and one O atom combines to form one molecule H2O. Here one H2 molecule means what? two H atoms which weigh 2.014g/mole ( molar mass of two H atoms) and one O atom means what? molar mass of one O atom is 16g/mole. So my question is one H atom means 1.007g H atom and one O atom means 16g O atom which represents the molar mass of one H atom and one O atom.
And
My second question is If we look at the periodic table and find the mass of H. We find the mass of H is 1.007. Here my question what does 1.007 mean? it means 1.007 g/mole, the molar mass of one H atom?

 

[DrDu]

What should I say from this equation? I think we say one H2 molecule(two H atoms) and one O atom combines to form one molecule H2O.

No, it doesn't, at least not only so.

Let me start differently: Let's look at a simple equation, e.g. $E=1/2 m v^2$. Wenn we write E for energy here, we do not say nothing about it's units. It could be Joules, mJ or kcal, or some atomic unit like eV (electron Volt). The same with chemical equations. If we write $\mathrm{2H_2 + O_2 \to 2H_2O}$, $\mathrm{H_2}$ stands for Hydrogen in its molecular form, but not necessarily for 1 molecule of hydrogen. It can stand for one mole, 1 kilomole, or one atom or one dozen atoms.

 

[CWatters]

+1

The equation tells you the ratio of the constituents.

The periodic table gives the mass in grams of one mole of the element (Molar mass).

If you want to calculate the mass of one molecule (eg it's molecular mass) you normally calculate the mass of one mole (it's molar mass) by adding up the molar masses from the periodic table in the right ratios and then divide by the number of molecules in a mole (Avogadro's number).

 

[Indranil]

No, it doesn't, at least not only so.

Let me start differently: Let's look at a simple equation, e.g. $E=1/2 m v^2$. Wenn we write E for energy here, we do not say nothing about it's units. It could be Joules, mJ or kcal, or some atomic unit like eV (electron Volt). The same with chemical equations. If we write $\mathrm{2H_2 + O_2 \to 2H_2O}$, $\mathrm{H_2}$ stands for Hydrogen in its molecular form, but not necessarily for 1 molecule of hydrogen. It can stand for one mole, 1 kilomole, or one atom or one dozen atoms.

I got your point but here I have a question below
''It can stand for one mole, 1 kilomole, or one atom or one dozen atoms''
Does it always (one atom, one mole, one molecule etc in an equation) give the mass in gram of one mole of the element (molar mass)?

 

[CWatters]

This is basic maths. If you multiply one side of an equation by 1000 you must also multiply the other. The units must also balance.

So if one side is in "grams per mole (molar mass)" then so is the other side. If one side is in "atoms" then the other side must also be in "atoms". If one side is in "kg" then so is the other side. If one side is in "elephants," then so is the other. You can't have 3 elephants + 2 elephants = 5 horses.

 

[DrClaude]

This is not my question. My question is simple. What should I say from the equations below?
1. H2 + O = H2O
My first question is
What should I say from this equation? I think we say one H2 molecule(two H atoms) and one O atom combines to form one molecule H2O. Here one H2 molecule means what? two H atoms which weigh 2.014g/mole ( molar mass of two H atoms) and one O atom means what? molar mass of one O atom is 16g/mole. So my question is one H atom means 1.007g H atom and one O atom means 16g O atom which represents the molar mass of one H atom and one O atom.
And
My second question is If we look at the periodic table and find the mass of H. We find the mass of H is 1.007. Here my question what does 1.007 mean? it means 1.007 g/mole, the molar mass of one H atom?

There are a few things I would like to comment on here.

When you look at the periodic table, what is given is the molar mass of the atoms, which includes relative isotopic abundance. Take hydrogen, for instance. You will find that the number is 1.007 97 g/mol. That means that if you collect 1/2 mole of hydrogen gas (H₂), which is the natural form for that element, such that you have a total of 1 mole of H atoms, that sample is going to have a mass of 1.007 97 g.

But if you divide that mass by Avogadro's number, you get 1.67377×10^-24 g, which is not the mass of one hydrogen atom. The mass of the most common isotope of hydrogen, ¹H, is actually 1.007 825 032 23 g/mol, or 1.67353×10^-24 g for one atom. This is because 0.0115% of hydrogen atoms are the deuterium isotope, ²H.

While the difference is small for hydrogen, it is not far all elements. A good example is chlorine. The periodic table will give a molar mass of 35.453 g/mol, but an actual sodium atom will either have a mass of 34.969 g/mol (³⁵Cl) or 36.966 g/mol (³⁷Cl). A sample of naturally occurring chlorine will be 75.8% ³⁵Cl and 24.2% ³⁷Cl.

 

[Indranil]

There are a few things I would like to comment on here.

When you look at the periodic table, what is given is the molar mass of the atoms, which includes relative isotopic abundance. Take hydrogen, for instance. You will find that the number is 1.007 97 g/mol. That means that if you collect 1/2 mole of hydrogen gas (H₂), which is the natural form for that element, such that you have a total of 1 mole of H atoms, that sample is going to have a mass of 1.007 97 g.

But if you divide that mass by Avogadro's number, you get 1.67377×10^-24 g, which is not the mass of one hydrogen atom. The mass of the most common isotope of hydrogen, ¹H, is actually 1.007 825 032 23 g/mol, or 1.67353×10^-24 g for one atom. This is because 0.0115% of hydrogen atoms are the deuterium isotope, ²H.

While the difference is small for hydrogen, it is not far all elements. A good example is chlorine. The periodic table will give a molar mass of 35.453 g/mol, but an actual sodium atom will either have a mass of 34.969 g/mol (³⁵Cl) or 36.966 g/mol (³⁷Cl). A sample of naturally occurring chlorine will be 75.8% ³⁵Cl and 24.2% ³⁷Cl.

'1.67353×10-24 g for one H atom or one H proton'?

 

[DrClaude]

'1.67353×10-24 g for one H atom or one H proton'?

Atom. The mass of the proton is 1.6726219 × 10^-24 g. The atom is heavier because of the presence of the electron.

 

[Indranil]

Atom. The mass of the proton is 1.6726219 × 10^-24 g. The atom is heavier because of the presence of the electron.

I knew that mass of an atom means the mass of protons and neutrons. So the H atom has one proton and one electron. So one proton weighs 1.6726219 × 10-24 g But you mentioned the difference value for mass for one H atom. Then the mass of one H atom does not mean mass of one proton of H atom?

 

[DrClaude]

Then the mass of one H atom does not mean mass of one proton of H atom?

What is "one proton of H atom"?

The mass of the hydrogen atom is the mass of the entire atom, namely the proton, the electron, and the mass equivalent to the binding energy (a hydrogen atom weighs less than the sum of the mass of a lone proton and a lone electron).

 

[Indranil]

What is "one proton of H atom"?

The mass of the hydrogen atom is the mass of the entire atom, namely the proton, the electron, and the mass equivalent to the binding energy (a hydrogen atom weighs less than the sum of the mass of a lone proton and a lone electron).

Then which one I use for the mass of one H atom 1.1.67353×10-24 g or 2 1.6726219 × 10-24 g. Could you suggest me?

 

[DrClaude]

Then which one I use for the mass of one H atom 1.1.67353×10-24 g or 2 1.6726219 × 10-24 g. Could you suggest me?

I said it already. The mass of one hydrogen atom, made up of 1 proton and 1 electron, is 1.1.67353×10^-24 g.

The mass of the most common isotope of hydrogen, 1H, is actually 1.007 825 032 23 g/mol, or 1.67353×10-24 g for one atom.

 

[Indranil]

I said it already. The mass of one hydrogen atom, made up of 1 proton and 1 electron, is 1.1.67353×10^-24 g.

Thank you all

 

[berkeman]

Thank you all

This sounds like a good place to close out the thread. Thank you to all who have tried to help @Indranil