# Writing Formulas

## Homework Statement

Write the formula for Ammonium Sulfide

NH4^+ = ammonium

S^2- = Sulfur

## The Attempt at a Solution

NH4^+2S

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CompuChip
Homework Helper
How many of each do you need to get something neutral?
Does 1 NH4 and 2 S have total charge 0?

Borek
Mentor
Quincy: final formula won't have charge inside. Could be you did OK, but ^+ are of no use here.

Try to format your formula properly using [ sub][ /sub] and [ sup][ /sup] tags (without spaces):

NH[ sub]4[ /sub][ sup]+[ /sup] = NH4+

## Homework Statement

Calculate the percentage composition of Silver (I) Oxide

Silver's atomic mass: 107.87

Oxygen's atomic mass: 16

## The Attempt at a Solution

Molecular mass: 123.87

(107.87/123.87) * 100 = 87.08% = Percent composition for Silver

(16/123.87) * 100 = 12.92% = Percent composition for Oxygen

Borek
Mentor
You are half OK and half wrong. Approach is correct, but molar mass is wrong.

What is formula of the silver (I) oxide?

You are half OK and half wrong. Approach is correct, but molar mass is wrong.

What is formula of the silver (I) oxide?
Ag2O?

Borek
Mentor
Yes, so what is the molar mass?

molar mass = 231.74?

percent comp of Silver = (215.74/231.74) * 100 = 93.10%?

percent comp of Oxygen = (16/231.74) * 100 = 6.90%?

Borek
Mentor
3*ok

P4S10 -- Phosphorus Sulfide?
Hg2O2 -- Mercury Oxide? -- and shouldn't the formula be HgO?...

Borek
Mentor
Check phosphorus sulfide article in wikipedia. Your answer is correct, but reality is much more complicated.

If Hg2O2 is HgO, same trick should be done to P4O10, converting it to P2O5. However, we know for sure that single molecule of these compounds is larger then its experimental formula shows.