Conditions Affect Chemical Reactions

Question 1

Equilibrium

Answer 1

The stage of a chemical reaction in which both reactants and products are present and their concentrations no longer change.

Question 2

Factors that Influence Reaction Rates I

Answer 2

Reaction rates can be altered by changing the conditions of a reaction. Changing factors such as: pressure, concentration of reactants and products, temperature, and the presence of catalysts will change the speed of a reaction. All these conditions can be applied to an equation to assess the rate of reaction. Ex: Temperature rises , the rate of endothermic (heat absorbed) will increase. However, when temperature rises an exothermic reaction (heat is released ) will slow down.

Question 3

Factors that Influence Reaction Rates II

Answer 3

Increasing the pressure surrounding a gas phase reaction increases the chance of collisions between atoms and molecules. This will increase the reaction rate. Increasing the concentration of reactants increases the probability that reactants will come in contact with each other, thus increasing the likelihood of breaking or creating a bond. If product concentration is increased the reaction will slow down.

Question 4

Chemical Equilibria

Answer 4

Not all chemical reactions will go to completion. ZnS + 2HCl -> ZnCl2 + H2S. Reactions written this way are assumed to go to completion. 1 mole of ZnS would react with 2 moles of HCl. When the reaction stops there is no remaining reactant. Only two products are present. However, many reactions are reversible and go to equilibrium, NOT completion. At equilibrium both reactants and products are present and their concentrations no longer change.

Question 5

Chemical Equilibrium Equation

Answer 5

CO + 3H2 -><- CH4 + H20. Once equilibrium is reached the rate of formation of CH4 and H20 equals the rate of formation of CO and 3H2.

Question 6

Catalysts

Answer 6

A substance that increases the rate of a chemical reaction without undergoing permanent chemical change by lowering the activation energy required for the reaction to occur. The activation energy is the minimum energy needed to initiate the reaction. Catalysts speed up reactions that would otherwise be slow to occur. Catalyst does not change during reaction and can be reused. They are mostly proteins called enzymes, which speed up chemical reactions within the body. Ex: amylase is a catalyst for the breakdown of starch polymers to glucose monomers. Helps body digest startches.

Question 7

Endothermic

Answer 7

Involving the absorption of heat and shift to the right as temperature rises.
A + B + Heat -><- C+D

Question 8

Exothermic

Answer 8

Involving the release of heat and shift to the left upon temperature increase. A + B -><- C+D+ Heat

Question 9

Chemical Equilibrium in Biological Processes

Answer 9

Many biological processes like the binding of O2 to hemoglobin, are equilibrium reactions or processes. In the lungs oxygen levels are high, O2 binds to hemoglobin. In tissues where oxygen is consumed by metabolism, O2 levels are low. Hb + 4O2 -><- HB(O2)4

Question 10

Factors that affect Equilibrium

Answer 10

Levels or concentrations of reactants and products, along with temperature and pressure, are some of the factors that affect equilibrium. When a chemical reaction is perturbed in responds by going in a direction in order to restore equilibrium. This is known as Le Chateliers Principle. Ex: In the lungs O2 binds to hemoglobin, Inhalation causes O2 blood concentration to rise, driving the reaction to the right. In tissue that is undergoing metabolism, O2 is consumed, reactant in this process is disappearing and the reaction shifts to the left.

Question 11

Catalysts

Answer 11

Catalysts are chemicals that lower