Question

Which one of the following is a balanced equation? A. Na (s) + O2 (g) → Na2O B. Zn (s) + HCl (g) → ZnCl2 (s) + H2 (g) C. Na (s) + MgF2 → 2NaF (s) + Mg (s) D. 2Na (s) + MgF2 → 2NaF (s) + Mg (s)

Answer 1

The answer is D

Explanation:

because it has equal numbers of each element on both sides of the equation ( 2 Na atoms on both the left hand and the right hand side, 1 Mg atom on each side, and 2 F atoms on each side)

Answer 2

If you were faced with this problem when you got change for a cash transaction you would immediately get the correct answer...

Explanation:

A balanced chemical equation requires equality of mass and equality of mass with respect to products and reactants...

We gots...

`A.` `Na(s) + O_2(g) rarr Na_2O(s)`...clearly not a winner...the balanced chemical equation should read...

`2Na(s) + 1/2O_2(g) rarr Na_2O(s)`

`B.` `Zn(s) + HCl(aq) rarr ZnCl_2(aq) + H_2`...clearly not a winner...the balanced chemical equation should read...

`Zn(s) + 2HCl(aq) rarr ZnCl_2(aq)+H_2(g)`

`C.` `Na(s) + MgF_2(s) stackrel(Delta)rarr 2NaF(s) + Mg`...clearly not a winner...the balanced chemical equation should read...

`2Na(s) + MgF_2(s) stackrel(Delta)rarr 2NaF(s) + Mg(s)`

`D.` `2Na(s) + MgF_2(s) stackrel(Delta)rarr 2NaF(s) + Mg(s)`..BOTH MASS and CHARGE are CONSERVED...we gots a winner...mass and charge are stoichiometrically balanced, as is every real chemical reaction.