Consider the balanced chemical equation,

mgcl2(aq) + 2agf(aq) → 2agcl(s) + mgf2(aq)

if both reactants are completely consumed and we produce 20 formula units of agcl, how many ions of mg and f did we start with?

a) 10 ions of mg and 20 ions of f

b) 10 ions of mg and 10 ions of f

c) 20 ions of mg and 10 ions of f

d) 20 ions of mg and 20 ions of f

  The number   of  ions   of Mg  and F  that   started is

 10 ions  of Mg  and 20   ions    of F  ( answer A)

Explanation

MgCl2 (aq)  + 2 AgF(aq) →  2AgCl(s)  + MgF2 (aq)

from equation  above  the  mole  ratio  of MgCl2  :AgCl  is 1 :2 therefore the number  of Mg ions  =  20  x 1 /2  = 10  ions

The   mole ratio  of  AgF: AgCl is  2:2  therefore  the  number  of F ions

  =20 ion  x2/2  = 20  ions

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