CHM 1025C Module Five Sample Answers        Name:__ Answers ____

Part H1 Double Replacement Reaction:

            Neutralization/Gas Forming Reactions              10 points         

 

Given the following Solubility Rules for Ionic Compounds:

 

Complete and balance the following precipitation reactions using the above solubility table

(write no reaction if both products are soluble or a covalent compounds is not formed)

 

1.   First write the ions of the products:

       Mg(OH)2 (s)    +    H2SO4 (aq)  ------> Mg2+  SO42-    +    H1+      OH 1-

 

      Second write the balanced formulas of the products and then

 balance the chemical equation:

       Mg(OH)2 (s)    +    H2SO4 (aq)  ------> MgSO4 (aq) +   2 H2O (l)

 

 

2.    H3PO4 (aq)  +   KOH (aq)  ------>  K1+      PO43-       +      H1+       OH1-      

 

       H3PO4 (aq)  +  2 KOH (aq)  ------>  K3PO4 (aq)      +   3 H2O (l)

 

 

3.    NH4NO3 (aq)  +   Ba(OH)2 (aq)  ----> Ba2+    NO31-     +      NH41+        OH1-

 

      2 NH4NO3 (aq)  +   Ba(OH)2 (aq)  ----> Ba(NO3)2 (aq) +    2  NH4OH (d)

(d) means immediate decomposes into ammonia and water

 

 2 NH4NO3 (aq)  + Ba(OH)2 (aq)  ----> Ba(NO3)2 (aq) +    2  NH3   +   2 H2O (l)

 

 

4.   HBr (aq)  +   Pb(CO3)2  (aq) ----->  Pb2+     Br1-    +    H1+      CO3 2-

 

     2 HBr (aq)  +   Pb(CO3)2  (aq) ----->  PbBr2   +    H2CO3 (d)

(d) means immediate decomposes into Carbon Dioxide and water

 

2 HBr (aq)  +   Pb(CO3)2  (aq) ----->  PbBr2   +   CO2    +  H2O(l)

 

5.    LiOH (aq)    +  H3PO4 (aq)     ---> Li1+      PO43-       +      H1+       OH1-

 

     3 LiOH (aq)    +  H3PO4 (aq)     --->     Li3PO4 (aq)      +    3 H2O (l)

 

When either H2CO3 or NH4OH is formed as a product it immediately

decomposes thus demonstrating a gas forming reaction. Most books

do not show the either H2CO3 or NH4OH as products, just the

decomposed products of the gases and water as in the final answer.