# Homework Help: Writing Formulas

1. Jul 8, 2008

### Quincy

1. The problem statement, all variables and given/known data
Write the formula for Ammonium Sulfide

2. Relevant equations
NH4^+ = ammonium

S^2- = Sulfur

3. The attempt at a solution

NH4^+2S

2. Jul 8, 2008

### CompuChip

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

3. Jul 8, 2008

### Staff: 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+

4. Jul 17, 2008

### Quincy

1. The problem statement, all variables and given/known data
Calculate the percentage composition of Silver (I) Oxide

Silver's atomic mass: 107.87

Oxygen's atomic mass: 16

3. 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

5. Jul 17, 2008

### Staff: Mentor

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

What is formula of the silver (I) oxide?

6. Jul 17, 2008

### Quincy

Ag2O?

7. Jul 18, 2008

### Staff: Mentor

Yes, so what is the molar mass?

8. Jul 18, 2008

### Quincy

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%?

9. Jul 21, 2008

### Staff: Mentor

3*ok

10. Aug 8, 2008

### Quincy

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

11. Aug 9, 2008

### Staff: 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.