<span>12.4 g
First, calculate the molar masses by looking up the atomic weights of all involved elements.
Atomic weight manganese = 54.938044
Atomic weight oxygen = 15.999
Atomic weight aluminium = 26.981539
Molar mass MnO2 = 54.938044 + 2 * 15.999 = 86.936044 g/mol
Now determine the number of moles of MnO2 we have
30.0 g / 86.936044 g/mol = 0.345081265 mol
Looking at the balanced equation
3MnO2+4Al→3Mn+2Al2O3
it's obvious that for every 3 moles of MnO2, it takes 4 moles of Al. So
0.345081265 mol / 3 * 4 = 0.460108353 mol
So we need 0.460108353 moles of Al to perform the reaction. Now multiply by the atomic weight of aluminum.
0.460108353 mol * 26.981539 g/mol = 12.41443146 g
Finally, round to 3 significant figures, giving 12.4 g</span>
There are 8 total hydrogen (H) atoms.
VSEPR notation gives a general formula for classifying chemical species based on the number of electron pairs around a central atom. However, not all species have the same molecules.
For example, carbon dioxide and surfer dioxide are both species, but one is linear and another one is bent.
POH = - log [OH]
<span>pOH = - log (6.40 × 10-3) </span>
<span>pOH = 2.19 </span>
<span>pH + pOH = 14 </span>
<span>pH = 14 - pOH </span>
<span>pH = 14 - 2.19 </span>
<span>pH = 11.8</span>