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What is the net ionic equation for the reactions of:a.) magnesium metal and acetic...

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nerdygirl-1996 | Student, Undergraduate | (Level 1) Honors

Posted April 14, 2013 at 3:13 AM via web

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What is the net ionic equation for the reactions of:
a.) magnesium metal and acetic acid
b.) acetic acid and ammonia solution

My answers were :
a.) Mg(s) + 2H+ (aq) -> Mg2+ (aq) + H2 (g)
b.) H+ (aq) + NH3(aq) -> NH4+ (aq)

Apparently these answers are wrong. Can someone please explain to me why?Please respond ASAP! 

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llltkl | College Teacher | (Level 3) Valedictorian

Posted April 14, 2013 at 4:17 PM (Answer #1)

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When magnesium metal reacts with acetic acid (CH3CO2H, a weak acid), magnesium acetate (a salt) and hydrogen gas is produced. The salt, Mg(CH3CO2)2 is soluble in water because all acetates are soluble. Thus, the complete equation is:

Mg(s) + 2 CH3CO2H(aq)  =  Mg(CH3CO2)2(aq)  + H2 (g)

Since acetic acid is a weak acid it should not be shown dissociated in the total ionic or the net ionic equation.  Mg(CH3CO2)2(salt)  is a strong electro­lytes.  The total ionic equation therefore is:

Mg(s) + 2 CH3CO2H(aq) =Mg˄+(aq) + 2CH3CO2 ˄– (aq) + H2 (g)

Following similar arguments, the total ionic equation of the second reaction can also be obtained.

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