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# Why......equation watch

1. 2CH3COOH + MgCO3 -- > (CH3COO-)2 Mg2+ + H2O + CO2

I know numbers are used to balance equations.
But why do we need the two outside the brackets?? Is it to balance the charge between COO- (1) and Mg2+ (2)?
Because without the 'twos' being used, there are equal numbers of H, C, and O on each side of equation!
2. (Original post by ILoveUSA)
2CH3COOH + MgCO3 -- > (CH3COO-)2 Mg2+ + H2O + CO2

I know numbers are used to balance equations.
But why do we need the two outside the brackets?? Is it to balance the charge between COO- (1) and Mg2+ (2)?
Because without the 'twos' being used, there are equal numbers of H, C, and O on each side of equation!
There are two different laws in operation.

1. The law of constant composition. This tells you that every compound has a fixed formula.

2. The law of conservation of matter. This tells you that you have to balance equations.

So when constructing equations you first must make sure all of the formulae are correct.

Then you balance using coefficients in front of the formula.
3. It shows that there's 2 of the whole ethanoate ion in the magnesium ethanoate rather than a single 2- charged ion which it could look like in your form or two oxygens if it was subscripted next to an O (eg, as in H2O where the subscripted 2 shows 2 hydrogens as opposed to Ca(OH)2 where it shows there is two of the hydroxide ion).

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