<Chemistry> I can't understand any of this topic Please help me...?

Question

Solve the molar mass and percentage Oxygen of the following compounds

1.H2SO4

2.Al2O2

3.BaO

4.BaSO4

5.Ch3COOH

6.Al(NO3)3

7.ZnSO4

8.Ba(C2H3O2)2

9.Na2Co3*10H2O

10.NaHCO2

the numbers are the subscripts thanks for helping... ^^

Answer 1

Okay, lets take this one step at time and look at number 1.

H2SO4

In 1 mole of this molecule, you have 2 H, 1 S, 4 O since you based the number on the subscript. Thus, you have 2 moles of Hydrogens, 1 moles Sulfur, and 4 moles Oxygens (based on the symbols). Make sense so far?

When you apply the concept of molar mass to a compound, it means the mass of one mole of molecules. The molar mass in grams per mole is numerically equivalent to the molecular mass or formula mass in atomic mass units (symbol: u).

In this case, all you want to do is use a Periodic Table to find the mass of Hydrogen, Sulfur, and Oxygen. When you do that, you see:

Hydrogen mass= 1.0079

Sulfur mass= 32.006

Oxygen mass= 15.9994

So, to find the molar mass, you merely have to multiply the number of the particular atom by its mass.

2(1.0079) + 1(32.006) + 4(15.9994)= 98.078 grams/mol

Got it?

Now, to find the percentage of oxygen, you basically want to do this:

Mass of oxygen in molecule/mass of molecule  X 100%

OR

(number of oxygens X mass of 1 oxygen)/(molar mass) X 100%

4(15.9994)/98.078  X 100%= 65.25%

I hope that helps.

Answer 2

i can&#039;t solve all but i can solve the first one as an example.

molar mass of H2SO4:98,078g

in 98.078 gr H2SO4 there are 64 grams of oxygen so as percentage 100x64/98.078=%65.25

Answer 3

For the molar mass, you merely look up the &#039;mass&#039; of each element. You can find this on the periodic table.  The subscript indicated the number of each atom.

i.e. H2SO4&#039;s molar mass

= H- (1.008 x 2) + S- (32.066 x 1) + O- (15.999 x 4) = 98.078

You then see that Oxygen, designated by O, is present in 4 per molecule. You take the total number of grams of oxygen:

4 x 15.999= 63.996

And divide this quantity of oxygen/ total mass x 100%

This gives you:

63.996g/98.078g =  .6592 x 100%= 65.92%

Good luck!!