# Chemistry question help!!

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absterlmao1

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Hello, i am currently transitioning from Y11 to Y12 and have a question on something. Am I right in saying that the mass of a 1H atom is 1/6.022x10^23, in other words... 1.66057781 because mass of an atom = Ar of element / Avogadro constant? and the mass of one mol of 3 H atoms is 1.660 etc from earlier multiplied by Avogadro's constant to get 1? Could I also just use mass = mol x Mr to work out 1 mol x the Mr of 3H which is just 1? 1x1 = 1? Then what about the mass of a H+ ion? is it just the mass of a proton? eg: 1.6726x10^-24?

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JA03

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(Original post by

Hello, i am currently transitioning from Y11 to Y12 and have a question on something. Am I right in saying that the mass of a 1H atom is 1/6.022x10^23, in other words... 1.66057781 because mass of an atom = Ar of element / Avogadro constant? and the mass of one mol of 3 H atoms is 1.660 etc from earlier multiplied by Avogadro's constant to get 1? Could I also just use mass = mol x Mr to work out 1 mol x the Mr of 3H which is just 1? 1x1 = 1? Then what about the mass of a H+ ion? is it just the mass of a proton? eg: 1.6726x10^-24?

**absterlmao1**)Hello, i am currently transitioning from Y11 to Y12 and have a question on something. Am I right in saying that the mass of a 1H atom is 1/6.022x10^23, in other words... 1.66057781 because mass of an atom = Ar of element / Avogadro constant? and the mass of one mol of 3 H atoms is 1.660 etc from earlier multiplied by Avogadro's constant to get 1? Could I also just use mass = mol x Mr to work out 1 mol x the Mr of 3H which is just 1? 1x1 = 1? Then what about the mass of a H+ ion? is it just the mass of a proton? eg: 1.6726x10^-24?

mass = moles x Mr

number of particles = moles x Avogadro's constant

moles = concentration x volume.

You weren't working out the mass of the hydrogen ion, you seem to have been trying to work out the number of particles but your equations were mixed. I suggest taking it step by step. If need be, you can post another question.

Just remember that A-Level Chemistry is a huge jump from GCSE. Mark schemes are so much more specific, there are more topics and the one thing that needs to be done before you think about that is to go through what you learnt at GCSE because that is your knowledge base for AS and A2.

Do not fret about the big jump because everyone initially struggles - I did but I overcame that and I ended up getting a B in my AS exam! (highest grade you can get at AS is an A) - Just don't stress too much, print out the specification, do some background reading - most of the moles calculations are the same so you can practice those first!

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absterlmao1

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TypicalNerd

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**absterlmao1**)

Hello, i am currently transitioning from Y11 to Y12 and have a question on something. Am I right in saying that the mass of a 1H atom is 1/6.022x10^23, in other words... 1.66057781 because mass of an atom = Ar of element / Avogadro constant? and the mass of one mol of 3 H atoms is 1.660 etc from earlier multiplied by Avogadro's constant to get 1? Could I also just use mass = mol x Mr to work out 1 mol x the Mr of 3H which is just 1? 1x1 = 1? Then what about the mass of a H+ ion? is it just the mass of a proton? eg: 1.6726x10^-24?

Dividing the relative mass of a species by Avogadro’s constant gives you the mass of a single particle in grams. There was actually a GCSE exam question (Q9e) in Edexcel’s june 2018 paper 1 (triple higher) where you had to use this method.

Dimensionally (i.e in terms of units) this works, as the units of relative mass are g/mol and the units of Avogadro’s constant are 1/mol:

(g/mol) / (1/mol) = g/mol x mol = g

So the mass of a single 1H atom in grams can be estimated using such a method, as the relative mass of 1H is 1 g/mol.

The mass of 1 mole of 3H atoms is actually 3 grams. This is because the relative mass of 3H is 3 g/mol (hence the 3). We can again check this dimensionally:

3 g/mol x 1 mol = 3 g

The difference between 1H and 3H is that 3H contains two neutrons (which add mass) and 1H has no neutrons. Both however, contain 1 proton, as they are isotopes.

And yes, it is reasonable to assume that a H+ ion does have an identical mass to a proton.

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absterlmao1

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@JA03 has already answered this very competently, but I reckon I can give further assistance.

Dividing the relative mass of a species by Avogadro’s constant gives you the mass of a single particle in grams. There was actually a GCSE exam question (Q9e) in Edexcel’s june 2018 paper 1 (triple higher) where you had to use this method.

Dimensionally (i.e in terms of units) this works, as the units of relative mass are g/mol and the units of Avogadro’s constant are 1/mol:

(g/mol) / (1/mol) = g/mol x mol = g

So the mass of a single 1H atom in grams can be estimated using such a method, as the relative mass of 1H is 1 g/mol.

The mass of 1 mole of 3H atoms is actually 3 grams. This is because the relative mass of 3H is 3 g/mol (hence the 3). We can again check this dimensionally:

3 g/mol x 1 mol = 3 g

The difference between 1H and 3H is that 3H contains two neutrons (which add mass) and 1H has no neutrons. Both however, contain 1 proton, as they are isotopes.

And yes, it is reasonable to assume that a H+ ion does have an identical mass to a proton.

**TypicalNerd**)@JA03 has already answered this very competently, but I reckon I can give further assistance.

Dividing the relative mass of a species by Avogadro’s constant gives you the mass of a single particle in grams. There was actually a GCSE exam question (Q9e) in Edexcel’s june 2018 paper 1 (triple higher) where you had to use this method.

Dimensionally (i.e in terms of units) this works, as the units of relative mass are g/mol and the units of Avogadro’s constant are 1/mol:

(g/mol) / (1/mol) = g/mol x mol = g

So the mass of a single 1H atom in grams can be estimated using such a method, as the relative mass of 1H is 1 g/mol.

The mass of 1 mole of 3H atoms is actually 3 grams. This is because the relative mass of 3H is 3 g/mol (hence the 3). We can again check this dimensionally:

3 g/mol x 1 mol = 3 g

The difference between 1H and 3H is that 3H contains two neutrons (which add mass) and 1H has no neutrons. Both however, contain 1 proton, as they are isotopes.

And yes, it is reasonable to assume that a H+ ion does have an identical mass to a proton.

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TypicalNerd

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This is a perfect response thank you so much I understand now. Bringing the units into it made it a lot clearer. As for the exam question, I didn't do triple science I did the single IGCSE Chemistry so these kinds of questions to do with Avogadro's number are completely new to me. Thanks again.

**absterlmao1**)This is a perfect response thank you so much I understand now. Bringing the units into it made it a lot clearer. As for the exam question, I didn't do triple science I did the single IGCSE Chemistry so these kinds of questions to do with Avogadro's number are completely new to me. Thanks again.

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JA03

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**absterlmao1**)

This is a perfect response thank you so much I understand now. Bringing the units into it made it a lot clearer. As for the exam question, I didn't do triple science I did the single IGCSE Chemistry so these kinds of questions to do with Avogadro's number are completely new to me. Thanks again.

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