Question

balancing equations
starting with the skeleton equations, balance the following equations by adding
coefficients where appropriate.

1. h₂ + f₂ → hf
2. sn + o₂ → sno
3. mgcl₂ → mg + cl₂
4. kno₃ → kno₂ + o₂
5. bn + f₂ → bf₃ + n₂
6. cui₂ + fe → fei₂ + cu
7. li + h₂o → lioh + h₂
8. nh₃ + o₂ → n₂ + h₂o
9. v₂o₅ + ca → cao + v
10. c₉h₆o₄ + o₂ → co₂ + h₂o
11. h₂s + pbcl₂ → pbs + hcl
12. c₃h₇oh + o₂ → co₂ + h₂o
13. zn + cuso₄ → cu + znso₄
14. c₆h₁₂o₆ + o₂ → co₂ + h₂o
15. c₂h₅oh + o₂ → co₂ + h₂o
16. al + h₂so₄ → h₂ + al₂(so₄)₃
17. fecl₃ + ca(oh)₂ → fe(oh)₃ + cacl₂
18. pb(no₃)₂ + k₂cro₄ → pbcro₄ + kno₃
19. cd(no₃)₂ + (nh₄)₂s → cds + nh₄no₃
20. ca(oh)₂ + nh₄cl → nh₃ + cacl₂ + h₂o

Explanation:

Step1: Balance hydrogen and fluorine atoms

For \(H_2 + F_2 ightarrow HF\), there are 2 hydrogen atoms and 2 fluorine atoms on the left - hand side. On the right - hand side, we need 2 \(HF\) molecules to balance the atoms. So the balanced equation is \(H_2+F_2 = 2HF\).

Step2: Balance oxygen and tin atoms

For \(Sn+O_2 ightarrow SnO\), there are 2 oxygen atoms on the left. So we need 2 \(SnO\) on the right. Then we also need 2 \(Sn\) on the left. The balanced equation is \(2Sn + O_2=2SnO\).

Step3: Check for decomposition reaction balance

For \(MgCl_2 ightarrow Mg + Cl_2\), the number of magnesium and chlorine atoms is already balanced. So the equation \(MgCl_2=Mg + Cl_2\) is balanced.

Step4: Balance oxygen atoms

For \(KNO_3 ightarrow KNO_2+O_2\), let's use the least - common - multiple method. The number of oxygen atoms: on the left, there are 3 in \(KNO_3\), on the right, there are \(2 + 2n\) (where \(n\) is the coefficient of \(O_2\)). We find that \(2KNO_3=2KNO_2 + O_2\) balances the equation.

Step5: Balance boron, nitrogen and fluorine atoms

For \(BN+F_2 ightarrow BF_3+N_2\), we first balance nitrogen: \(2BN+F_2 ightarrow 2BF_3+N_2\). Then balance fluorine: \(2BN + 3F_2=2BF_3+N_2\).

Step6: Check for single - displacement reaction balance

For \(CuI_2+Fe ightarrow FeI_2+Cu\), the number of copper, iron and iodine atoms is balanced. So \(CuI_2+Fe = FeI_2+Cu\).

Step7: Balance hydrogen and lithium atoms

For \(Li + H_2O ightarrow LiOH+H_2\), we first balance hydrogen. \(2Li+2H_2O = 2LiOH + H_2\).

Step8: Balance nitrogen and hydrogen atoms

For \(NH_3+O_2 ightarrow N_2+H_2O\), balance nitrogen: \(2NH_3+O_2 ightarrow N_2+H_2O\). Then balance hydrogen: \(2NH_3+O_2 ightarrow N_2 + 3H_2O\). Finally, balance oxygen: \(4NH_3+3O_2=2N_2+6H_2O\).

Step9: Balance oxygen, calcium and vanadium atoms

For \(V_2O_5+Ca ightarrow CaO+V\), balance oxygen: \(V_2O_5+5Ca ightarrow 5CaO+V\). Then balance vanadium: \(V_2O_5+5Ca = 5CaO+2V\).

Step10: Balance carbon, hydrogen and oxygen atoms

For \(C_9H_6O_4+O_2 ightarrow CO_2+H_2O\), balance carbon: \(C_9H_6O_4+O_2 ightarrow 9CO_2+H_2O\). Balance hydrogen: \(C_9H_6O_4+O_2 ightarrow 9CO_2+3H_2O\). Balance oxygen: \(C_9H_6O_4+\frac{19}{2}O_2=9CO_2+3H_2O\), multiply through by 2 to get \(2C_9H_6O_4 + 19O_2=18CO_2+6H_2O\).

Step11: Balance sulfur, lead and chlorine atoms

For \(H_2S+PbCl_2 ightarrow PbS+HCl\), balance chlorine: \(H_2S+PbCl_2=PbS + 2HCl\).

Step12: Balance carbon, hydrogen and oxygen atoms

For \(C_3H_7OH+O_2 ightarrow CO_2+H_2O\), balance carbon: \(C_3H_7OH+O_2 ightarrow 3CO_2+H_2O\). Balance hydrogen: \(C_3H_7OH+O_2 ightarrow 3CO_2+4H_2O\). Balance oxygen: \(C_3H_7OH+4O_2=3CO_2+4H_2O\).

Step13: Check for single - displacement reaction balance

For \(Zn+CuSO_4 ightarrow Cu+ZnSO_4\), the number of zinc, copper, sulfur and oxygen atoms is balanced. So \(Zn + CuSO_4=Cu+ZnSO_4\).

Step14: Balance carbon, hydrogen and oxygen atoms

For \(C_6H_{12}O_6+O_2 ightarrow CO_2+H_2O\), balance carbon: \(C_6H_{12}O_6+O_2 ightarrow 6CO_2+H_2O\). Balance hydrogen: \(C_6H_{12}O_6+O_2 ightarrow 6CO_2+6H_2O\). Balance oxygen: \(C_6H_{12}O_6+6O_2=6CO_2+6H_2O\).

Step15: Balance carbon, hydrogen and oxygen atoms

For \(C_2H_5OH+O_2 ightarrow CO_2+H_2O\), balance carbon: \(C_2H_5OH+O_2 ightarrow 2CO_2+H_2O\). Balance hydrogen: \(C_2H_5OH+O_2 ightarrow 2CO_2+3H_2O\). Balance oxygen: \(C_2H_5OH+3O_2=2CO_2+3H_2O\).

Step16: Balance aluminum, hydrogen, sulfur and oxygen atoms

For \(Al+H_2SO_4 ightarrow H_2+Al_2(SO_4)_3\), balance aluminum: \(2Al+H_2SO_4 ightarrow H_2+Al_2(SO_4)_3\). Balance sulfate groups: \(2Al + 3H_2SO_4=3H_2+Al_2(SO_4)_3\).

Step17: Balance iron, chlorine, calcium and hydroxide atoms

For \(FeCl_3+Ca(OH)_2 ightarrow Fe(OH)_3+CaCl_2\), balance chlorine: \(2FeCl_3+Ca(OH)_2 ightarrow 2Fe(OH)_3+CaCl_2\). Balance hydroxide: \(2FeCl_3+3Ca(OH)_2=2Fe(OH)_3+3CaCl_2\).

Step18: Balance lead, nitrogen, oxygen, potassium and chromium atoms

For \(Pb(NO_3)_2+K_2CrO_4 ightarrow PbCrO_4+KNO_3\), balance potassium and nitrogen: \(Pb(NO_3)_2+K_2CrO_4=PbCrO_4 + 2KNO_3\).

Step19: Balance cadmium, nitrogen, oxygen, sulfur and ammonium atoms

For \(Cd(NO_3)_2+(NH_4)_2S ightarrow CdS+NH_4NO_3\), balance ammonium and nitrate: \(Cd(NO_3)_2+(NH_4)_2S=CdS + 2NH_4NO_3\).

Step20: Balance calcium, chlorine, nitrogen, hydrogen and oxygen atoms

For \(Ca(OH)_2+NH_4Cl ightarrow NH_3+CaCl_2+H_2O\), balance chlorine: \(Ca(OH)_2+2NH_4Cl ightarrow NH_3+CaCl_2+H_2O\). Balance nitrogen: \(Ca(OH)_2+2NH_4Cl ightarrow 2NH_3+CaCl_2+H_2O\). Balance hydrogen and oxygen: \(Ca(OH)_2+2NH_4Cl=2NH_3+CaCl_2+2H_2O\).

Answer:

1. \(H_2+F_2 = 2HF\)
2. \(2Sn + O_2=2SnO\)
3. \(MgCl_2=Mg + Cl_2\)
4. \(2KNO_3=2KNO_2 + O_2\)
5. \(2BN + 3F_2=2BF_3+N_2\)
6. \(CuI_2+Fe = FeI_2+Cu\)
7. \(2Li+2H_2O = 2LiOH + H_2\)
8. \(4NH_3+3O_2=2N_2+6H_2O\)
9. \(V_2O_5+5Ca = 5CaO+2V\)
10. \(2C_9H_6O_4 + 19O_2=18CO_2+6H_2O\)
11. \(H_2S+PbCl_2=PbS + 2HCl\)
12. \(C_3H_7OH+4O_2=3CO_2+4H_2O\)
13. \(Zn + CuSO_4=Cu+ZnSO_4\)
14. \(C_6H_{12}O_6+6O_2=6CO_2+6H_2O\)
15. \(C_2H_5OH+3O_2=2CO_2+3H_2O\)
16. \(2Al + 3H_2SO_4=3H_2+Al_2(SO_4)_3\)
17. \(2FeCl_3+3Ca(OH)_2=2Fe(OH)_3+3CaCl_2\)
18. \(Pb(NO_3)_2+K_2CrO_4=PbCrO_4 + 2KNO_3\)
19. \(Cd(NO_3)_2+(NH_4)_2S=CdS + 2NH_4NO_3\)
20. \(Ca(OH)_2+2NH_4Cl=2NH_3+CaCl_2+2H_2O\)