Posted by Bobby on Wednesday, July 21, 2010 at 10:01pm.
1. The delta Hf of an element in its standard state is defined to be
a) 0 kJ/mol
b) 10 kJ/mol
c) -10 kJ/mol
d) greater than 0 kJ/mol
e) a unique value for each element
I am assuming its a?
You should be SURE it's a.
2. Which of the following statements are true?
I) The reaction vessel cools when an endothermic reaction occurs.
II)An endothermic reaction has a negative value of delta H.
III)Heat is liberated when an exothermic reaction occurs.
a) I and II
b) I, II, and III
c) I and III only
d) II and III only
e) none of them
I am thinking that it's d?
No. Exothermic means heat is given off. Endothermic means heat is absorbed. d isn't correct. III is correct. II can't be correct. By definition exothermic reactions have - delta H and endothermic is + delta H. So the only other choice is I and that is correct, also. When the reaction absorbs heat it must take it from somewhere. The most obvious choice is from it's surroundings and that's the reaction container. So the container gets cold.
3. Which factor does not affect the rate of a chemical reaction in aqueous solution?
a) The enthalpy change of the reaction
b) The activation energy of the reaction
c) The collision frequency of the reaction particles
d) The relative orientation of the colliding particles
e) The temperature of the solution.
It's a?yes
4. Which of the following processes are exothermic?
I) Boiling water
II) Freezing water
III) Condensing steam
IV) Melting ice
a) I and II only
b) II and III only
c) I and IV only
d) II, III, and IV only
e) II and IV only
it's b?yes
5. Which statement about an activate complex is true?
a) It is a stable substance
b) It has lower chemical potential energy, or enthalpy, than reactants or products.
c) It occurs only in endothermic reactions
d) It occurs at the transition state of the reaction
e) It always breaks down to form product molecules.
I am assuming it's d?I would go with d
6. A catalyst changes the
I) Mechanism of a reaction
II) Enthalpy change of a reaction
III) Activation energy of a reaction
a) I only
b) III only
c) I and III only
d) II and III only
e) I, II, and III
I think it's b I don't know about this since the directions are not clear. III is correct but since the word only appears I assume more than one of the answers can be correct. I would argue that a catalyst could change the mechanism of the reaction by allowing the reactants to form an "intermediate complex."
Related Questions
ap chemistry - Carbon monoxide reacts with oxygen to form carbon dioxide by the...
AP Chem - The energy change H associated with the reaction NBr3(g) + 3H2O(g...
Chemistry - For a particular reaction at 195.1 °C, ΔG = -1488.09 kJ...
Chemistry II - Saw this one already answered, but did not understand at all... ...
chemistry - N204 (l) Delta Hf (kJ/mol) = -20 E cell S (J/mol.K) = 209 N204(g) ...
chem - calculate the delta Hf of c6h12o6 (s) from the following data: Delta H ...
Chemistry - "Given that the bond enthalpy of the carbon-oxygen bonds in ...
Chemistry - Predict whether the following reactions will be exothermic or ...
ap chem - The heat of combustion of propane is -2,220.1 kJ/mol calculate the ...
chemistry - A 79.9-L sample of a gaseous hydrocarbon, measured at 1.00 atm ...
For Further Reading
