Question

I will medal who ever answers!
Which of the following does NOT have to have an octet of valence electrons to be stable?
a) F
b) Na
c) Cl
d) Fe
4. _____ An element with the electron configuration 1s2
2s2
2p6
3s2
3p6
4s2 will ionize to form a _____.
a) Anion
b) Cation
c) Neutral atom
d) None of the above
19. _____ The empirical formula of a compound is CH, and its molar mass is 78.12 g/mol. What is
the molecular formula of the compound?
a) CH
b) C2H2
c) C4H4
d) C6H6

Answer 1

1. Not sure about this one. :/ Sorry

4. B. Cation

The element with this electron configuration is Ca, which ionizes to become a positive ion (also known as a cation).

19. D. C6H6

To obtain the molecular formula (MF), multiply all elements in the empirical formula (EF) by n, where...

n = (molar mass of actual compound)/(molar mass of EF compound)

Note that the molar mass of the actual compound is given to be 78.12 g/mol.

Find the molar mass of the EF compound by adding the molar mass of C and the molar mass of H.

molar mass of EF comound = 12.01 g/mol + 1.008 g/mol = 13.02 g/mol

Now find n:

n= (78.12 g/mol)/(13.02 g/mol) = 6

Multiply all elements in the EF by 6:

6 x (CH) = C6H6

Therefore, the molecular formula is C6H6.