Answer:
The number of moles =

The number of molecules =

Explanation:
Volume of the sphere is given by :

here, r = radius of the sphere


Radius = 3 mm
r = 3 mm
1 mm = 0.01 dm (1 millimeter = 0.001 decimeter)
3 mm = 3 x 0.01 dm = 0.03 dm
r = 0.03 dm
<em>("volume must be in dm^3 , this is the reason radius is changed into dm"</em>
<em>"this is done because 1 dm^3 = 1 liter and concentration is always measured in liters")</em>



(1 L = 1 dm3)
Now, concentration "C"=
The concentration is given by the formula :

This is also written as,

moles
One mole of the substance contain "Na"(= Avogadro number of molecules)
So, "n" mole of substance contain =( n x Na )

Molecules =

molecules
Based on the chemical equation, 4 moles of lithium reacts with 1 mole of oxygen to produce 2 moles of lithium oxide.
First of all you need to find 1 mole of Lithium by diving 1.68 mol by 4 and the answer should be 0.42 mol. To calculate the no. of moles of lithium oxide, you've to multiply 0.42 mol by 2. Hence the answer, 0.84 mol.
There are three number of electrons lost by 1 mole of aluminium because aluminum has +3 charge on it.
<h3>What is cation?</h3>
When an atom loses electron, positive charge appears on the atom this is called cation. In this reaction we can see that aluminium has +3 charge which means that it loses 3 electrons.
So we can conclude that There are three number of electrons lost by 1 mole of aluminium because aluminum has +3 charge on it.
Learn more about electron here: brainly.com/question/23390564
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N = m/M
Where,
n = number of moles
m = mass of substance
M = molar mass of substance
0.8286 = m / 30.067
Multiply both sides by 30.067
m = 24.9135162g