Help please

[Modyasoo1]

Can anyone tell me why pls

-Each Mole of ammonia gas(Nh3) contains

Answer:One mole of nitrogen atoms why pls?


Each mole of sodium nitrate Nano3 contains

1 mole of sodium ions why?



and please


37%Nitrogen n =14 63%Oxygen O=16 the empirical formula?



0.02Mole of Carbon C=12 0.04Mole of Hydrogen H=1 the empirical formula please?

[Dark*Phantom]

Answer to questions 1 and 2
Each mole of NH4 contains one mole of nitrogen because no numbers are written after nitrogen
Example: One mole of H2SO4 contains 2 moles of hydrogen, one mole of sulphur and 4 moles of oxygen

Answer to question 3
Let's suppose that the mass of the compound in 100g
Mass of oxygen = 63 gm
Mass of nitrogen = 37 gm
Molar mass of oxygen = 16 gm
Molar mass of nitrogen = 14 gm
No. of moles in oxygen = 63 / 16 = 3.9375 moles
No. of moles in nitrogen = 37 / 14 = 2.643 moles
The ratio between nitrogen and oxygen = 2.643 : 3.9375 = 1 : 1.5 = 2 : 3

The empirical formula is N2O3

Answer to question 4
No. of moles in carbon = 0.02
No. of moles in hydrogen = 0.04
Ratio between carbon and hydrogen =0.02 : 0.04 = 1:2

The empirical formula is CH2

[Modyasoo1]

thanks and can you tell me

Why it's one mole of nitrogen atoms why it's not one mole of nitrogen molecules or ions?


And something more..

How i know if 1=2 and 1.5=3 in the empirical formula because sometimes 1=1 like CH2

Here Carbon is 1

And here C2H3

Carbon is 1 too
and Hydrogen is 1.5

how to know that please and thanks

[Dark*Phantom]

Answer 1
We studies in 1st prep that the molecules of non metals (such as nitrogen) have two atoms. Which means that nitrogen molecule contains 2 nitrogen atoms. Thus, molar mass of nitrogen element (pure nitrogen gas) = 14 + 14 = 28gm. While molar mass of nitrogen , in case it is in other compounds is 14gm

When nitrogen exists in a compound, say nitric acid HNO3, it exists in the form of atoms only. If we said that there is one nitrogen molecule (instead of atom) in nitric acid, we mean that there are two nitrogen atoms - which is wrong. Moreover, atoms (not molecules) bind to each other forming molecules

We cannot say nitrogen ions because the compound didn't dissolve in water

So, we should say "Nitrogen atoms" because of the previous reasons

Answer 2
There is an important rule that we should take in consideration when solving empirical formula questions, which is

The simplest ratio between the atoms forming a compound in an empirical formula should be in whole numbers, not decimals or fractions

In other words, ratios which contain fractions such as 1 :1.5 cannot be used in empirical formula, it is impossible to say that the empirical formula of an organic compound is CH1.5 because we cannot get one and half hydrogen atoms

Thus, we should multiply both sides of the ratio with a number to get the simplest ratio in whole numbers

Example:-
If the ratio between sodium and oxygen in a compound is 2:2.5

To get rid of the decimals, we find the lowest common multiple of both sides, which is 2

The ratio = 4:5

I hope I helped you, Good Luck

[hamada90]

at first we should determine the type of compound(covalent or inon1-
2- in cas of covalent compound we use the word atom as NH3
3-n cas of ionic compound we use the word ionas NaCL

[dr.micl]

Firstly , this is my first post here in this nice forum, i'd like to add an answer for the questions stated above: considering the first qu. i think you are confused in the point of when we choose ions / atoms or molecules, it's quite easy
- Molecule is the large unit which is composed of either ions or atoms , we say ions when the molecule is ionic (contains an ionic bond) e.g. table salt NaCl - MgO - PbBr2 and we say atoms when the molecule is covalent (contains covalent bonds) e.g. NH3 - H2O
You can easily know if the molecule is ionic or covalent if you know that all ionic molecules have metal ion in the beginning , look at NaCl , sodium metal - and also magnesium and lead in the other examples while covalent molecules are formed between non-metals
IF this is useful , please inform,