Aqueous Chemistry

Question 1

what is the enthalpy of a chemical reaction that is spontaneous at 37° C and has an entropy change of 35 J* K -1mol -1?
A) 5.6 kj/mol
B)10.8 kj/mol
C)35 kj/mol
D)62.4 kj/mol
E) not enough information

Answer 1

E) not enough information

Gibbs free energy is given by: delta G= delta H -T delta S
In the question we have provided the values of T and delta S. However,there are still tow variables that are known ( delta G and delta H). All we know is that delta G is negative, this is not enough information to solve for delta H. By setting delta G to 0, we could calculate that the enthalpy must be less than 10 785 J/ mole, but we cannot get a more specific answer.

Question 2

For a given reaction, 18. 6 kj* mol of heat is absorbed and the change in entropy is 62 J * K* mol -1. What is the lowest temperature above which the reaction will be spontaneous?
A) 300 K
B)294 K
C)3K
D)43 K
E) 308 K

Answer 2

A) 300 K

Question 3

Which of the following statements is false?
A) hydrogen bonds are weaker than covalent bonds
B)ionic interactions do not depend on the relative orientation of ions
C)van der waals interactions are too weak to be a significant attractive force
D) hydrogen bonding strength depends on the orientation of the atoms involved.
E)ionic interactions are stronger in strength depends on the orientation of the atoms involved

Answer 3

C) van der waals interactions are too weak to be a significant attractive force

Question 4

Which one of the following is NOT an example of a hydrogen bond?
A) -N-H——-N
B)-O-H——N
C)-C-H——O
D)-O-H——-O
E)-N-H——O

Answer 4

C) -C-CH——O