Question

practice problems: rules for equations: a) atoms must be equal on both the reactant and product side of the equation. b) you cannot change the subscripts!!!! c) add coefficients in front of atoms and molecules one at time. d) if your 1st attempt does not work try again! fecl₃ + naoh → fe(oh)₃ + nacl p + o₂ → p₂o₅

Explanation:

Step1: Balance the equation $P + O_2

ightarrow P_2O_5$
First, balance the phosphorus atoms. There are 2 phosphorus atoms in $P_2O_5$. So put a 2 in front of $P$ on the left - hand side: $2P+O_2
ightarrow P_2O_5$. Then, balance the oxygen atoms. There are 5 oxygen atoms in $P_2O_5$ and 2 oxygen atoms in $O_2$. The least - common multiple of 2 and 5 is 10. So we need 5 $O_2$ molecules and 2 $P_2O_5$ molecules. The balanced equation is $4P + 5O_2=2P_2O_5$.

Step2: Balance the equation $FeCl_3+NaOH

ightarrow Fe(OH)_3 + NaCl$
Balance the chlorine atoms first. There are 3 chlorine atoms in $FeCl_3$. So we need 3 moles of $NaCl$ on the right - hand side: $FeCl_3+NaOH
ightarrow Fe(OH)_3 + 3NaCl$. Then, balance the sodium atoms. Since we have 3 moles of $NaCl$, we need 3 moles of $NaOH$ on the left - hand side. The balanced equation is $FeCl_3 + 3NaOH=Fe(OH)_3+3NaCl$.

Answer:

a) $4P + 5O_2 = 2P_2O_5$
b) $FeCl_3+3NaOH = Fe(OH)_3 + 3NaCl$