How do I find how many moles of HF it takes to react completely with 4.90 mol of SiO2? Thanks! 4 HF(g)+SiO2(s) ---> SiF4(g)+2H2O(l)

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72

the ratio of the conjugate base to the acid required to attain the desired ph.