Name Counting Atoms Worksheet Directions for each problem:
1) write down the different elements in each compound.
2) write down how many of that particular atom there are
3) how many atoms are there total in the compound.

Examples:

LiOH 2 NaCl3 5 Si(SO4 ) 3 NH2O2
Li - Na – Si – N -
O - Cl – S – H -
H – O - O -
Total: Total: Total: Total:

1) NaOH 6) 4 HNO3 11) 4 MgOH

2) MgCl2 7) 4 Li2O 12) 2 NaOH

3) Li2SO4 8) 3 H2O 13) 4 Al2SO3

4) NaC2H3O2 9) 3 Al2O3 14) 2 NH4PO4

5) NH4Cl 10) 6 C6 H12 O6 15) 5 ZnSO4

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

it has both hydrogen and oxygen