K.+Soo+Single+displacement+reaction.

=** Single Displacement Reaction. **= == = = A single displacement reaction is characterized by one element replacing another similar element in a compound; the free element of the reactants displaces the more similar ion of the product’s compound and the other ion becomes the uncombined element.

** Formula. **
A + BC —›  B + AC

** Example of a single displacement reaction. **
Magnesium co mbines with hydrochloric acid to produce hydrogen gas and magnesium chloride.

** Changing the word equation into a formula equation… **
The first step in going from the written equation to the formula equation is to determine the atomic symbols of your reactants and products. Magnesium is represented by “Mg”, hydrochloric acid would be “HCl”, hydrogen is “H”, and magnesium chloride, “MgCl”. Using these atomic symbols, write your formula equation: Mg + HCl —›  H + MgCl Hydrogen is diatomic, so you know you need to add a subscript of 2 after the product H.

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Mg + HCl —› H2 + MgCl Now check to see if compounds are written correctly because the charges of compounds always have to equal zero (note: this only appl ies to the compounds because any element by itself automatically has an oxidization number of 1). You know that HCl is written correctly because hydrogen has a charge of 1+ and chlorine has a charge of 1- (because H is in group 1 and Cl is in group 17). MgCl has to be changed however, because Mg has a charge of 2+ (because it is from group 2) and Cl only has a charge of 1-. To correct this, add a subscript 2 after the Cl. Mg + HCl  —› H2 + MgCl2  Now to balance: the magnesiums on either side of the equation are equal, however there are an unequal number of hydrogen and chlorine atoms. To balance the entire thing, you add a coefficient of 2 before the HCl on the left so that there are equal numbers of every element. Mg + 2 HCl —› H2 + MgCl2 The equation is balanced! Remember that you cannot change the subscripts to balance an equation, you can only add coefficients.

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