The heat of reaction for the process described in (a) can be determined by applying Hess's law. The heats of reaction shown in the table below can be obtained experimentally or looked up in tables of enthalpy data. Which two of these heats of reaction would be the easiest and safest to measure in the laboratory, and which two are better obtained through reference sources? Why?
Hint: Consider whether a reaction takes place in aqueous solution or instead involves noxious
gases.
Reaction
NH3(g) --> NH3(aq)
NH3(aq)+ HCI(aq)—> NH4+(aq)+Cl-(aq)
HCI(g)—>HCI(aq)
NH4Cl(s)—>NH4+(aq)+Cl-(aq)
Heat of reaction
AH=-36.64 kJ/mol
AH=-51.6 kJ/mol
AH=-75.14 kJ/mol
AH=+14.8 kJ/mol

each  column  of the  table  is called a group. elements in a group share similar properties. groups are  read  from  top  to  bottom. metal. metalloid. nonmetal. solid. liquid. gas. fe. hg. o.  2. 3. 4. 5. 6. 7. 8. 9.  2. beryllium. 9.012. 4.  sodium. 22.990.  11. 3.  magnesium. 24.305.  12.  potassium. 39.098.  19. 4.  calcium. 40.078.  20. i guess  i  

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.