Home
Class 12
CHEMISTRY
The standard enthalpy of formation of ga...

The standard enthalpy of formation of gaseous `H_(2)O` at 298 K is `-241.82` kJ/mol. Calculate `DeltaH^(@)` at 373 K given the following values of the molar heat capacities at constant pressure :
`H_(2)O(g)=33.58 " JK"^(-1)" mol"^(-1), " "H_(2)(g)=29.84 " JK"^(-1)" mol"^(-1), " "O_(2)(g)=29.37 " JK"^(-1)" mol"^(-1)`
Assume that the heat capacities are independent of temperature :

A

`-242.6 kJ/"mol"`

B

`+242.6 kJ//mol`

C

`+24.26` kJ/mol

D

`-242.6` J/mol

Text Solution

Verified by Experts

The correct Answer is:
A
`H_(2)(g) + 1/2O_(2)(g) to H_(2)O(g), Delta_(r)H^(@) (298 K) = -241 kJ//mol^(-1)`
`Delta_(r)H_(373K)^(@) = Delta_(r)H_(298 K)^(@) + DeltaC_(p) (T_(2)-T_(1)) =-241.8 + [(C_(p))_(H_(2)O) -(C_(p))_(H_(2)) -1/2(C_(p))_(O_(2))] (373 - 298)`
`=-[241.8 + (33.6 - 28.8) - 1/2 xx 29.4] xx (373 - 298) xx 10^(-3) =-242.6 kJ//mol`
Promotional Banner

Similar Questions

Explore conceptually related problems

The standard enthaply for the reaction H_(2)(g) + 1//2 O_(2)(g) to H_(2)O(l) is - 285.76 kJ at 298 K. Calculate the value of DeltaH at 373 K .The molar heat capcities at constant pressure (C_(P)) in the given temperature range of H_(2)(g),O_(2)(g) and H_(2)O(l) are respectively 38.83,16 and 75.312 JK^(-1) mol^(-1) .

The heat of formation of HCl at 348 K from the following data will be : 0.5H_(2)(g)+0.5Cl_(2)(g)toHCl " "DeltaH_(298)^(@)=-22060 cal. The mean heat capacities over this temperature range are, H_(2)(g)," " C_(p)=6.82 " cal" " mol"^(-1)K^(-1) Cl_(2)(g)," " C_(p)=7.71 " cal" " mol"^(-1)K^(-1) HCl(g)," " C_(p)=6.81 " cal" " mol"^(-1)K^(-1)

What is the value of change in internal energy at 1 atm in the process? H_(2)O(l,323K)rarrH_(2)O(g,423K) Given : C_(v,m)(H_(2)O,l)=75.0JK^(-1) mol^(-1):" "C_(p,m)(H_(2)O,g)=33.314JK^(-1)mol^(-1) DeltaH_(vap)"ar 373 K"=40.7KJ//mol