The average atomic mass of lithium is 6.941 amu.
The molecular mass of
is:
2·1 + 1·32 + 4·16 = 98 g/mol
The amount of solute, expressed by mol, is:

The molar concentration definition is: 
Doing the calculations:

(If you detect any mistakes in my English report me them, please).
Si -Atomic number -14 -1s2 2s2 2p6 3s2 3p2 - 4 valence electrons
Answer:
+3
Explanation:
The oxygen all have a -2 oxidation state. (peroxides are exceptions)
The chemical structure is symmetrical. Both carbon are equivalent.
2 (oxidation state of carbon) + 4 (oxidation state of oxygen) = charge of ion.
2 (oxidation state of carbon) + 4 (-2) = -2
oxidation state of carbon = +3