q3 gen chem quiz

the study of heat and energy changes that accompany physical and chemical processes.

It is not seen but its effects are obvious. Matter has this. It is produced from chemical reactions. Atoms and molecules have this; they possess kinetic and potential energy

states that energy can neither be created nor destroyed. It can only be transformed from one kind to another. The energy of the universe is constant.

FIRST LAW OF THERMODYNAMICS

•A change that involves absorption of energy from the surroundings is said to be an ??? change.
•When this change occurs, the temperature of the reaction mixture decreases since part of the kinetic energies of particles in the surroundings are absorbed for use in the reaction.

•Reaction that gives off heat
•to its surroundings
•A candle flame
•Rusting iron
•Making ice cubes
•Forming bonds

Reaction that absorbs heat
•from its surroundings
•Forming cation from atom in gas phase
•Producing sugar by photosynthesis
•Cooking an egg
•Melting ice cubes
•Breaking bonds

•If energy is released to the surroundings when a change occurs, such change is described as an ??? change.
•The heat released by this reaction often results to an increase in the temperature of the reaction mixture and the reaction vessel, and possibly the air surrounding the vessel.

TRUE OR FALSE? WHEN A CHEMICAL REACTION OCCURS:
•Energy is required to break chemical bonds
•Energy is released when bonds are formed

The energy contained within the system, referred to as ???, E, is simply the sum of the kinetic and potential energy of all the components of the system.

The total change in energy of a system, ΔE, is equal to the sum of the heat absorbed or evolved by the system, q, and the work performed by or done on the system, w, as expressed by the equation:

ΔE = q + w

Burning gasoline is a highly exothermic reaction. The total amount of heat obtained, which is actually the energy change when the reaction occurs, is called the ???

A concept related to heat of reaction is ???, H, which simply stated, refers to the heat transferred by a process that occurs at constant pressure.

•this accompanies chemical reaction is called heat of reaction.
•This is the net energy change resulting from the breaking and the making of bonds.
•It represents heat absorbed or evolved when the reactants are converted into products, at constant pressure.

•The heat released or absorbed when a reaction takes place is an important and integral part of the reaction, and could be indicated in the chemical equation.
•An equation which shows the heat involved is called a ???

or heat of formation, ΔHf, is defined as the enthalpy change when a substance is formed from its constituent element.

ΔHf˚, is the change in enthalpy for a reaction that forms 1 mole of a compound from its stable elements at their standard states.

For molecules to collide effectively, it is required that there is sufficient energy for the collision to occur.

The energy comes from the kinetic energy of the reacting molecules.

A2 + B2  A2B2  2AB

•The formation of A2B2 is crucial because it determines whether the reaction proceeds.
•The energy needed for the formation of A2B2 called an activated complex is called ???

•This is the energy needed for the formation of the activated complex and for the reaction to occur. This is also considered as the rate determined step because once this is formed, the product is formed immediately.

A2 + B2  A2B2  2AB

•The A2B2 is called a ??? and it determines how fast the reaction will occur.
•It is a short-lived molecule and, therefore, very unstable because from the top, it rolls down immediately to form the product AB.

ENERGY DIAGRAM
The difference of the energy of the reactants and the products is mathematically expressed as:

Factors affecting the rate of chemical reaction

An increase in the temperature of a reaction always causes the reactant particles to move more rapidly. Therefore, heating the reactants allows more frequent collisions among particles.

Concentration refers to the number of particles of a substance in a given volume.
•When the concentration increases, the frequency of collisions is increased and the reaction speeds up.

•When solid reactants are present in very small pieces, reaction rates can increase considerably. The tinier pieces have greater surface area so they provide much greater contact of the reactants and effect more collisions.

•A ??? is a substance that increases the rate of chemical reaction without being used up in the reaction.
•This may be recovered unchanged at the end of the process.

Many industrial processes depend upon catalytic procedures, but even more important to humans are the natural catalyst known as ???.

??? are biological catalyst that enable the chemical reactions in living organisms to proceed enormously faster than they would in a test tube.

In order for the reaction above to take place, the molecules A2 must collide with the molecules of B2. Once the A2 comes in contact with B2, a short-lived molecule A2B2 is formed. The bonds of A2 and B2 are destroyed and new bonds are formed. The rearrangement of bonds of the starting molecules will cause the formation of a new substance AB.

A2 + B2  A2B2  2AB

Only ??? will result to the formation of a product. For an effective collision to occur, there must be a proper orientation of the reactants during collision.

Two reactant particles approach each other then fly apart because they are not correctly oriented for a reaction to occur.

Fast moving, energetic molecules correctly oriented from new substances.

+The greater the number of collisions, the greater chances of effective collisions, and the greater the amount of products formed per unit time.
+Therefore, the greater the number of molecular collision, the faster the reaction rate.

•An enzyme is a ???.
•A ??? is a substance that speeds up a reaction and does not appear in the overall chemical equation.
• A ??? offers an alternative pathway by which a reaction occurs

•The substance in yeast that converts the sugar to alcohol is an ???.
•??? are present in the body and are responsible for reactions that extract energy from food we eat.
•They increase the speed of reactions essential to life.

•The presence of a ??? lowers the activation energy needed to be overcome for the reaction to occur and forms another activated complex.
•For the reaction: A2 + B2  A2B2  2AB
•In the presence of a catalyst (C), the reaction proceeds in a differential pathway as shown below:
A2 + C A2C + B2  2AB + C

•The catalyst C is regenerated at the end of the reaction.
•The alternative pathway will need a ???
•At ???, more collisions will have sufficient energy to pass over the energy barrier.

TRUE OR FALSE: Important Characteristic Features of Catalysts
•A catalyst does NOT initiate a chemical reaction.
•A catalyst does not be consumed in the reaction.
•Catalysts tend to react with reactants to form intermediates and at the same time facilitate the production of the final reaction product. After the whole process, a catalyst can regenerate.

The reaction which involves a catalyst in their system are known as catalytic reactions.

•Catalysts which increase the rate of a chemical reaction are ??? catalysts.
•It increases the rate of reaction by lowering the activation energy barriers such that a large number of reaction molecules are converted into products, thereby the percentage of yield of products increases.

•Catalysts which decrease the rate of reaction are ??? catalyst.
•It decreases the rate of reaction by increasing the activation energy barrier which decreases the number of reactant molecules to transform into products and hence the rate of reaction decreases.

this is an example of? Example (??? Catalyst):
Decomposition of Hydrogen peroxide into water and oxygen is retarded by using Acetanilide, this acts as a negative catalyst to decrease the rate of decomposition of hydrogen peroxide

•If the products of a chemical reaction is act as catalyst and it catalyzed the reaction then the reaction is called auto catalyzed reaction and the produced compound is called auto catalyst.

this is an Example of (??? Catalyst):
When nitric acid is poured on copper, the reaction is very slow in the beginning, gradually the reaction becomes faster due to the formation of nitrous acid during the reaction which acts as an auto-catalyst.

•A substance that influences the speed of a reaction which is not possible under ordinary conditions.

this is an Example of (??? Catalyst):
•Sodium sulphite solution readily oxidises in air, but sodium arsenite solution does not oxidise by passing air in the solution. When both these solutions are mixed and air is passed then both the substances get oxidised.

Types of catalyst

this is an Example of ( ??? Catalyst)
In the preparation of NH3 by Haber’s process, iron oxide acts as a positive catalyst and increases the yield of ammonia in spite of less reaction of Nitrogen