ix. _____ h₂ + p₂ → _____ ph₃\nx. _____ p + _____ cl₂ → _____ pcl₃\nxi. _____ mg + o₂ → _____ mgo\nxii…

Explanation:

Step1: Balance hydrogen and phosphorus in $H_2 + P_2\rightarrow PH_3$

Set coefficients: $3H_2+P_2 = 2PH_3$

Step2: Balance phosphorus and chlorine in $P + Cl_2\rightarrow PCl_3$

Set coefficients: $2P + 3Cl_2=2PCl_3$

Step3: Balance magnesium and oxygen in $Mg + O_2\rightarrow MgO$

Set coefficients: $2Mg+O_2 = 2MgO$

Step4: Balance potassium and bromine in $K + Br_2\rightarrow KBr$

Set coefficients: $2K + Br_2=2KBr$

Step5: Balance gold and oxygen in $Au_2O_3\rightarrow Au + O_2$

Set coefficients: $2Au_2O_3=4Au + 3O_2$

Step6: Balance zinc and oxygen in $Zn + O_2\rightarrow ZnO$

Set coefficients: $2Zn+O_2 = 2ZnO$

Step7: Balance hydrogen and sulfur in $H_2S\rightarrow H_2 + S_2$

Set coefficients: $2H_2S=2H_2+S_2$

Answer:

ix. $3H_2 + P_2\rightarrow 2PH_3$ x. $2P+3Cl_2\rightarrow 2PCl_3$ xi. $2Mg + O_2\rightarrow 2MgO$ xii. $2K + Br_2\rightarrow 2KBr$ xiii. $2Au_2O_3\rightarrow 4Au+3O_2$ xiv. $2Zn + O_2\rightarrow 2ZnO$ xv. $2H_2S\rightarrow 2H_2 + S_2$