Answer:
because a mosquito net prevent mosquito bites
<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>
The molarity of Sr(OH)2 solution is = 0.1159 M
calculation
write the equation for reaction
that is, Sr(OH)2 +2HCl→ SrCl2 + 2 H2O
then finds the mole of HCl used
moles = molarity x volume
=40.03 x0.1159 = 4.639 moles
by use of mole ratio between Sr(OH)2 to HCL which is 1 :2 the moles of Sr(OH)2 is therefore = 4.639 x1/2 = 2.312 moles
molarity of Sr(OH)2 is = moles / volume
=2.312 /20 =0.1159 M
1.Electrons can be transferred from one atom to another.
2.Electrons can be shared between neighbouring atoms.
3.Electrons can be shared with all atoms in a material.
