January 27, 2015

Homework Help: Chemistry

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?

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?

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?

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?

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?

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

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