Explanation:
here's the answer to your question about
They all are correct , so with that being said anyone of them can be right
The number of moles of moles of Magnesium,chlorine and oxygen atoms in 7.80 moles of Mg(ClO4)2 is calculated as below
find the total number of each atom in Mg(ClO4)2
that is mg = 1 atom
Cl = 1x2 = 2 atoms
O = 4 x2 = 8 atoms
then multiply 7.80 moles with total number of each atom , to get the number moles of each atom
that is
Mg = 7.80 x1= 7.80 moles
cl = 7.80 x2=15.6 moles
O = 7.80 x8= 62.4 moles
Answer: The given statement is true.
Explanation:
According to the Dalton's law, total pressure of a mixture of gases that do not react with each other is equal to the partial pressure exerted by each gas.
The relationship is as follows.

or, 
where,
....... = partial pressure of individual gases present in the mixture
Also, relation between partial pressure and mole fraction is as follows.

where,
= mole fraction
Thus, we can conclude that the statement Dalton's law of partial pressures states that the total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture, is true.
Method:
1) Find the atomic number in a periodic table: the number of electrons equal the atomic number
2) Use Aufbau rule
Element atomic number electron configuration
<span>
P 15 1s2 2s2 2p6 3s2 3p3
Ca 20 </span><span><span>1s2 2s2 2p6 3s2 3p6 4s2
</span>Si 14</span><span> 1s2 2s2 2p6 3s2 3p2
S 16</span><span><span> 1s2 2s2 2p6 3s2 3p4
</span>Ga 31. </span><span><span> 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p</span> </span>