Which set of coefficients will balance this chemical equation? __pbs(s) + __o2(g) → 2pbo(s) + 2so2(g)

A two in both of the blanks will balence the equation. It will look like so:

2PbS(s) + 2O2(g) --> 2PbO(s) +2SO2(g)

The balanced equation is:

2 PbS(s) + 3 O₂(g) → 2 PbO(s) + 2 SO₂(g)

Explanation:

The law of conservation of matter states that since no atom can be created or destroyed in a chemical reaction, the number of atoms that are present in the reagents has to be equal to the number of atoms present in the products.

Then, you must balance the chemical equation.

The subscripts next to each atom indicates the number of atoms in the equation. These must be added to observe the amount of each element on each side of the reaction. If the same atom appears in more than one molecule, you must add its quantities.

The coefficients located in front of each molecule indicate the amount of each molecule for the reaction. This coefficient can be modified to balance the equation, just as you should never alter the subscripts.

By multiplying the coefficient mentioned by the subscript, you get the amount of each element present in the reaction.  

So in this case you have:

__PbS(s) + __O₂(g) → 2 PbO(s) + 2 SO₂(g)

Left side:  1 lead (Pb), 1 sulfur (S) and 2 oxygen (O).

Right side:  2 lead (Pb), 2 sulfur (S) and 6 (2+2*2) oxygen (O)

__PbS(s) + 3 O₂(g) → 2 PbO(s) + 2 SO₂(g)

Left side:  1 lead (Pb), 1 sulfur (S) and 6 (3*2) oxygen (O).

Right side:  2 lead (Pb), 2 sulfur (S) and 6 (2+2*2) oxygen (O)

2 PbS(s) + 3 O₂(g) → 2 PbO(s) + 2 SO₂(g)

Left side:  2 lead (Pb), 2 sulfur (S) and 6 oxygen (O).

Right side:  2 lead (Pb), 2 sulfur (S) and 6  oxygen (O)

You can see that you finally have the same amount of each element on each side of the chemical reaction. So the balanced equation is:

2 PbS(s) + 3 O₂(g) → 2 PbO(s) + 2 SO₂(g)

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6