# GChem: No wonder I am not good at GChem..

#### IWantSmile

10+ Year Member
5+ Year Member
hi, I need a help again... please.... No wonder I am not good at GChem.

Here is the question: The percentage of an element X equal to 77.4%, 63.2%,69.6%, and 72%. If the compund with 77.4% X is XO, what is X, and what are the other compounds?

I will post the answer later.

#### IWantSmile

10+ Year Member
5+ Year Member
Ops! I figured it out the answer.
For someone who want to do anyway, here is the answer: MnO, MnO2,MnO3, and MnO4.

#### Contach

10+ Year Member
wow. why is it the hardest thing in the world to find a freaking periodic table of elements with atomic mass online...

that just took 5 minutes of my life.

#### Contach

10+ Year Member
Ops! I figured it out the answer.
For someone who want to do anyway, here is the answer: MnO, MnO2,MnO3, and MnO4.

ok, then i will not begin.
why don't you explain how it was done to ACTUALLY help the others?

#### supraman

##### Boston Celtics
10+ Year Member
7+ Year Member
wow. why is it the hardest thing in the world to find a freaking periodic table of elements with atomic mass online...

that just took 5 minutes of my life.

periodic table
view extra large images
click the pic

#### IWantSmile

10+ Year Member
5+ Year Member
ok, then i will not begin.
why don't you explain how it was done to ACTUALLY help the others?

OK.

Given question: The percentage of an element X equal to 77.4%, 63.2%,69.6%, and 72%. If the compund with 77.4% X is XO, what is X, and what are the other compounds?

I started 77.4% X is XO. If 77.4% is X then O is 22.6%. I used the ratio of X: O = 3.4 : 1. I know the MW of O is 16g; so, 16g * (3.4) = 54.9 g X
I looked at the periodic table for finding the element of X. That is Manganese, Mn.

For the 63.2% , If Mn is 63.2% then O is 36.8%. The calculation is basically same as above, using the ratio of Mn : O = 1.7 : 1
I know from previous information that MW of O has been increased; 2(16g O)* (1.7) (Mn/O)= 54.9g Mn ; MnO2.

Now you can try with other to get answer 69.6% and 72%.

#### Contach

10+ Year Member
periodic table
view extra large images
click the pic

and this is exactly what i did. all i got were atomic numbers, no atomic masses. had to look at like 10 before i found one with masses.

10+ Year Member
5+ Year Member
Bump

#### Contach

10+ Year Member

lol. why are you bumping a thread that's solved.