Question

How do you balance `Si(OH)_4 + NaBr -> SiBr_4 + NaOH`?

Answer 1

`"Si(OH)"_4+color(red)4"NaBr"` `rarr` `"SiBr"_4+color(blue)(4)"NaOH"`

The word equation is now, "One mole silicon tetrahydroxide plus four moles sodium bromide produce one mole silicon tetrabromide plus four moles sodium hydroxide."

Explanation:

Unbalanced Equation

`"Si(OH)"_4+"NaBr"` `rarr` `"SiBr"_4+"NaOH"`

The word equation for this reaction is, "Silicon tetrahydroxide plus sodium bromide produce silicon tetrabromide plus sodium hydroxide."

When balancing a chemical equation, we compare the numbers of atoms (or moles) of each element on both sides of the equation. If the number of each element is not the same, we can add coefficients in front of each formula.

Balancing the Equation

Think of `"OH"`, as a single species. There are 4 `"OH"` on the left and 1 on the right. To balance them, place a coefficient of `color(blue)4` in front of NaOH.

`"Si(OH)"_4+"NaBr"` `rarr` `"SiBr"_4+color(blue)(4)"NaOH"`

The `"OH"` is now balanced with 4 on each side.

There are now 4 `"Na"` atoms on the right side and 1 on the left. To balance them, place a coefficient of `color(red)4` in front of NaBr.

`"Si(OH)"_4+color(red)4"NaBr"` `rarr` `"SiBr"_4+color(blue)(4)"NaOH"`

There are now 4 sodium atoms on both sides, and there are also now 4 bromine atoms, `"Br"`, on both sides.

The equation is now completely balanced, having the same number of atoms (or moles) of each element on both sides: 1 Si, 4 O, 4 H, 4 Na, 4 Br.

Notice that I did not change the subscripts. I only changed the quantity of the species involved in the reaction by adding coefficients.