Question

When you add solid ammonium nitrate to water, the solution feels cold. Which statement best describes this observation?

a) NH4NO3(s)->NH4NO3(aq)+6.80 kJ

b) Nh4NO3(s)->NH4NO2(aq) delta = +6.80- kJ/ mole of NH4NO3

c)the reaction is exothermic

d) heat is released from the system so it feels colder

e) the work is performed by the chemical system to surroundings

The volume of a sample of nitrogen gas increase from 5 L to 15 L against a constant pressure of 25 atm. What is w in Joules for the gas given 1 atm L=101.3 J?

a) 250 J

b)-250 J

c) 25325 J

d)-25325 J

e)10 kJ

Answer 1

1) b is correct

Since solution becomes cold which means heat is absorbed which in turn means that reaction is endothermic and hence delta H = +ve

2) Initial volume V₁ = 5L

Final volume V_{2 =} 15L

Change in volume V = V₂ - V₁ = 10 L

Workdone W = - PV = - 25 atm 10 L = -250 atm L = -250 101.3 J = - 25325 J

Option D is correct