3.
Na₃PO₄ + ___ KOH ----> ___ NaOH + K₃PO₄
The first step to balance this equation is to determine the number of atoms of each element that we have on each side of the equation.
Na₃PO₄ + ___ KOH ----> ___ NaOH + K₃PO₄
Na: 3 Na: 1
P: 1 P: 1
K: 1 K: 3
H: 1 H: 1
O: 5 O: 5
We can start balancing the Na, we have 3 atoms on the left and 1 atom of right side of the equation. To balance the Na we can change the coefficient for NaOH and write a 3 there.
Na₃PO₄ + ___ KOH ----> 3 NaOH + K₃PO₄
Na: 3 Na: 3
P: 1 P: 1
K: 1 K: 3
H: 1 H: 3
O: 5 O: 7
The P is already balanced, but the K is not. We have 3 atoms on the right side of the equation but only 1 atom of the left. We can change the coefficient of KOH and write a 3 there.
Na₃PO₄ + 3 KOH ----> 3 NaOH + K₃PO₄
Na: 3 Na: 3
P: 1 P: 1
K: 3 K: 3
H: 3 H: 3
O: 7 O: 7
And the equation now is balanced.
Answer: Na₃PO₄ + 3 KOH ----> 3 NaOH + K₃PO₄
4,
__ P + O₂ ----> P₂O₂
O: 2 O: 2
P: 1 P: 2
In this one O is already balanced but P is not. We have two atoms of P on the right and only 1 on the left. We can write a 2 as the coefficient of P.
2 P + O₂ ----> P₂O₂
O: 2 O: 2
P: 1 P: 2
The equation is balanced.
Answer: 2 P + O₂ ----> P₂O₂