Question

balance each equation.

Mg(s)+HBr(aq) ------ MgBr2(s) + H2(g)

B. CO(g) + O2(g) ----------CO2 (g)

c. PbS (s) + O2 (g) ---------PbO (s) + SO2(g)

d.H2SO4 +NAOH -------- Na2SO4 +H2O

e. H3PO4 +Ca (OH)2--------CA3 (PO4)2+ H2O

Answer 1

a )Mg(s)+HBr(aq) ------ MgBr2(s) + H2(g)

The number of atoms at each side of the equation must be the same. So in order to equate both sides you have to multiple the stoichiometric coefficient until equate the number of atoms.

you have 2 Br in the right side you need to have the same number of atoms at the left one. So you multiply HBrX 2

Mg(s) + 2HBr (aq) -----------MgBr2 (s) + H2

1 Mg 2 H; 2 Br 1 Mg; 2 Br ; 2 H both sides are balanced

B. CO(g) + O2(g) ----------CO2 (g)

balance 1 C ; 3 O 1 C; 2 O you have to multiply CO and CO2 by 2, in this way the eq is :

2CO(g) + O2(g) ---------- 2 CO2 (g) is balanced

2C ; 4 O    2C ; 4 O

c) PbS (s) + O2 (g) ---------PbO (s) + SO2(g)

balance 1Pb; 1 S; 2 O 1 Pb; 3O; 1 S; since O is both in PbO and SO2 you have to multiply one of them in order to have a ever number of O. if you Put a 2 in PbO, you need to put a 2 on PbS and 2O2

2PbS (s) + 2O2 (g) ---------2 PbO (s) + SO2(g) (is balanced)

balance     2Pb; 2S; 4 O 2 Pb; 4O; 2 S;

d.H2SO4 +NAOH -------- Na2SO4 +H2O

balance 3 H, 1S; 5 O; 1 Na 2 Na, 1S, 2 H, 5 O there is 2 Na at the right, so multilplying x2 at left and 2 before H2O

d.H2SO4 +2 NAOH -------- Na2SO4 + 2 H2O

balance 4 H, 1S; 6 O; 2 Na 2 Na, 1S, 4 H, 6 O

e) H3PO4 +Ca (OH)2--------CA3 (PO4)2+ H2O

balance 5 H; 1P; 1 Ca; 6 O 3 Ca; 2 P; 9 O; 2H you need a 3 before Ca at the left, and since there is 2 PO4^3- at the right, you have to put a 2 before H3PO4

    e) 2H3PO4 +3Ca (OH)2-------- CA3 (PO4)2+ H2O

    12 H; 3P; 3 Ca; 14 O 3 Ca; 2 P; 9 O; 2H we need 6 H2O at the right

2H3PO4 +3Ca (OH)2-------- CA3 (PO4)2+ 6H2O (balanced)

12 H; 3P; 3 Ca; 14 O 3 Ca; 2 P; 14 O; 12H