The mantle has a mass of around
that is around 68.4% of earth's mass.
So to calculate moles we need to first find out the mass of oxygen and silicon present in mantle. It is given that oxygen is 44.8% by mass in mantle and 21.5% by mass in mantle, therefore to calculate its mass, we need to use 
Now, to calculate mass percentage of oxygen


Similarly the mass of silicon can be calculated

Now, the moles of any substance is calculated by


where, mass of oxygen in kilograms is 
So,
Similarly 

Now, to calculate mole ratio we need to divide every moles to the lowest calculated mole that is the moles of Si and round it off to the nearest whole number.





<span>The net ionic equation for the reaction of alum (KAl(SO4)2.12H2O.) and KOH is </span>the solid AlOH3 formed.
What classification system????
Quarts of pure antifreeze must be added to 5 quarts of a 20 antifreeze solution to obtain a 50 antifreeze solution is 3.
Antifreeze solution is a solute that lowers the freezing point of the liquid in a solution.
For calculating the amount of quarts of pure antifreeze solution added can be given by:
5×20/100 + x × 100% = (x+5) × 50/100
Where, x is the amount of antifreeze required for addition and pure antifreeze is 100% of the antifreeze taken.
1 + x = (x+5) 0.5
1 + x = 0.5x + 2.5
0.5x = 1.5
x = 3
So, 3 quarts of pure antifreeze must be added to 5 quarts of a 20 antifreeze solution to obtain a 50 antifreeze solution.
Learn more about Antifreeze solution here, brainly.com/question/14619701
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Answer:
178.01347 ± 0.00093 g/mol
Explanation: