Chemistry Exam 3

Which reaction would predict to have a higher likelihood of being product favored and why?

The Ea in the forward direction is smaller which favors the rate in the forward process increasing the likelihood it will be product favored

Which line represents the catalyzed reaction?

The bottom line because it has a lower activation energy

How would you explain that the reaction between methanol, water, and oxygen is exothermic?

The chemical bonds between atoms in the reactants are weaker than the chemical bonds between atoms in the products

Methanol can be directly decomposed into hydrogen gas and carbon monoxide. However, carbon monoxide may react with hydrogen to re-form methanol. Which of the two processes, the decomposition of methanol or the formation of methanol has higher configuration effectiveness during molecular collisions?

The decomposition of methanol

The more collisions in a given time:

The faster the process

The reaction of methanol with water to produce hydrogen has to be carries out at high temperatures, where the two reactants are in the gas phase. The pressure on the gases can also be controlled by changing the volume of the gas chamber. How would the rate of reaction change as the volume of the chamber decreases?

The rate of the reaction should increase

How would you expect the rate of the forward reaction to be impacted by changed in pressure within an organism?

The rate would increase with increasing pressure because there would be more collisions between reactants

Where is the Transition State?

Transition state is the top bump -in the middle of reaction

Imagine 60% of A goes to B, but only 30% of B goes to A. When does it stop?

Write out the whole chart

How do you find the Ea for a certain reaction?

You subtract energy of the reactants by the transition state (top) -Transition state minus Reactant

How do you find the Delta E for a certain reaction?

You subtract energy of the reactants from the energy of the products -Product minus Reactant

There are chemical processes that result in...

a net absorption of energy from the surroundings (endothermic reactions) and a net release of energy from the system to the surrounding (exothermic reactions)

Chemical processes always lead to....

a net transfer of energy between the system in which the reactions takes place and its surroundings

Collision theory states:

atoms/molecules must collide in order for chemical reactions to occur

For a chemical reaction to occur...

colliding particles must have enough energy to reach a transition state that leads to the formation of the new products (aka Ea or activation energy)

Endothermic

energy of a product is higher than that of the reactants

Exothermic

energy of the product is lower than that of the reactants

Chemical processes always result in...

energy transfer

Configuration Effectiveness

is the fraction of all possible collisions between reacting species in which particles meet at effective orientations for the reaction

While pH can influence the reaction rates of many biological reactions...

it is generally only relevant to acid-base reactions

The activation energy is the minimum...

required kinetic energy that particles must possess in order for a reaction to take place

UV-B leads to

tanning and sunburn

The higher the % of configurations that lead to effective collisions...

the faster the process -thus, the fewer the number of particles that need to interact to generate the products, the simpler the composition and structure of such particles, the faster the process

The higher the concentration of the particles

the larger the probability they will collide -this implies that the rate should decrease as reactants are consumed

The higher the % of effective configurations

the more likely the transformation

The lower the Ea

the more likely the transformation

The higher T:

the more particles have enough energy to react

The higher the Ea (activation energy)

the stringer the effect of T

When chemical reactions occur in closed environments...

the total mass of the system before and after the process remains constant (mass is conserved)

The kinetic energy distribution among particles changes with:

with the changing temperature

UV-A leads to

wrinkling and aging

What happens when you increase the reaction time? A+BC--> ABC

-adding a catalyst (less energy to react with each other) -increasing temperature (causing the reactants to move faster) -increasing the concentration of A and BC (increases rate at which they collide)

Where is Delta E and what does it mean/stand for?

-beginning of reaction -the reactants have some amount of potential energy (E) -it means the energy difference between reactants and products (the difference in energy between the reactants and the products)

Basic common features of chemical reactions:

-chemical reactions may involve one or more initial substances, called the reactants -as a result of he process, new chemical substances with different chemical composition are formed, called the products -reactants combine to form products in specific definite proportions

Rate of a reaction is determined by these three factors:

-collision frequency -configuration effectiveness -activation energy

What happens when you decrease the reaction time? A+BC--> ABC

-decreasing the concentration of A

How do you read an energy/reaction progress chart?

-from left to right -reactions on the left -products on the right

Reactions tend to speed up with both:

-increasing temperature -concentration of the reactive species

Name some true statements regarding energy changes during a reaction

-increasing the amount of reactants increases the number of collisions, and the reaction goes faster -reactants must collide, with proper orientation, with energy greater than or equal to the activation energy for a reaction to occur -decreasing the temperature decreases the kinetic energy of the reactants, and the reaction goes more slowly -the energy of a collision between atoms or molecules must be greater than or equal to the activation energy (Ea) for bonds to be broken -the greater the Ea, the slower the reaction, the lower the Ea the faster the reaction

How can you tell if it's a limiting reactant or not?

-it determines the maximum amount of products

Limiting reactant

-limits the amount of product that can form

Where is the Ea and what does it mean/stand for?

-needed to form from the transition state -stands for activation energy- energy needed to initiate the reaction

The energy of activation (Ea) is the difference between...

-the energy of the starting materials (the reactant) and the energy of the transition state (the top point/the middle)

The transformation of CH(3)OH into CO and H(2) is endothermic. Which process can be expected to occur at a faster rate? and why?

-the formation of CH(3)OH from CO and H(2)

What are some indications that a chemical process has occurred?

-the formation of one of more new chemical substances with a distinct composition -or a change in the net amounts of some chemical species in a closed system that a chemical process has occurred

What two factors determine whether a collision between 2 reactant molecules will result in a reaction?

-the particles must be in the correct orientation upon impact -the particles must collide with enough energy to meet the activation energy of the reaction

Heat increases:

-the rate at which particles collide and the force with which they collide and so it will usually increase the rate at which reactions occur. -but it isn't the deterring factor for it's occurrence

At the beginning of a reaction...

-the reactants have some amount of potential energy embedded within them. -the energy required to initiate the reaction is called the activation energy (the "energy barrier" between the reactants and products)

The energy change (Delta E) is the energy difference between...

-the starting materials (the reactants) and the products

Chemical reactions occur:

-when molecules or atoms collide, the bonds between atoms are broken and new bonds are formed -breaking bonds of reactants requires energy; bond formation releases energy

Chemical Equilibrium

1. at equilibrium, the rates of forward and reverse reactions are equal 2. Thus even though both reactions are occurring, reactions are still being converted to products and vice versa. -each species are being produced and consumed at the same time 3. There is no change in concentration, the concentrations of reactants and products remain constant

how many grams = 1 kg?

1000 grams= 1 kg

Write a balanced equation for the decomposition of aluminum chloride into its elements -how do you know how to find the subscript numbers?

2AlCl(3) ---> 2Al + 3Cl(2) -to find subscript numbers: s from periodic table left to right it goes: +1, +2, +3, blank, -3, -2, -1 So it's Al +3 and Cl-1 and you just criss cross the numbers

Draw out an energy and reaction progress diagram (aka an energy diagram) (or called a reaction coordinate)

:D

The hydrogen of unsaturated hydrocarbons is exothermic. This implies that:

A C-H bond is stronger than a C-C bond

What is another name for transition state?

Activated complex -in the middle

What happens when you add energy to the system? A+BC--> ABC

Adding energy to the system increases the rate of collisions between reactants.

What releases energy?

BOND FORMATIONNNN YAYAYAY

CFC's stand for:

Chlorofluorocarbons- they're the main source of Cl radicals in the atmosphere

Can Delta E be + 0r -? Can Ea be + or -?

Delta E can be positive or negative but activation energy is always positive

What increases the rate at which particles collide?

Heat does!

When a question asks what the maximum mass/amount, what does that mean?

Maximum amount= the smaller answer of the 2 equations

In order for a chemical reaction to take place:

Particles must collide but they must collide with the correct orientation

2KClO(3) ----> 2KCl + 3O(2) If this reaction produced 81.6 g of KCl, how much O(2) was produced in grams?

-First start by converting mass of KCl to moles using molar mass of KCl -grams to moles, moles to moles, moles to grams -for moles to moles, look at equation and use the big numbers from there -whatever was in the first part of the line, put it on the bottom. So if KCl was the first thing written, put it on bottom next and put O(2) on top -answer: 52.32 grams of O(2)

What substances are present in the reaction mixture when equilibrium has been obtained? 3H(2) + N(2) <----> 2NH(3) and why?

-H(2) -N(2) -NH(3) -both products and reactants are being produced and consumed at the same rate -this is chemical equilibrium -equilibrium reactions always have some concentration of each substance present because the reaction is never completed in either direction -the production of either products or reactants may be favored but none of the chemicals in the reaction will be completely consumed

What are the 7 diatomic elements?

-Hydrogen: H(2) -Nitrogen: N(2) -Oxygen: O(2) -Chorine: Cl(2) -Iodine: I(2) -Bromine: Br(2) -(Have No Fear Of Ice Cold Beer)

Do all chemical reactions of to completion?

-No -There can be times where the reactant fully transforms to a product -but other times where the final state involves the presence of constant amounts of both reactants and products

Mass conservation

-The chemical reaction leads to a re-arrangement of the atoms into new molecules -The mass does not change because all of the different atoms remain in the system

What is the forward and reverse process favored by?

-The forward process is favored by Ea -The reverse process is favored by configuration effectiveness

Do chemical reactions occur at varying speeds?

-Yes -the speed or rate of chemical processes depends on the chemical nature of the reactants, but also on factors such as temperature, pressure, and concentration of the reacting species

Can particles of the product chemically interact with each other?

-Yes they can -as reactants interact to generate products in a chemical reaction, particles of the products may chemically interact with each other and regenerate particles of the reactants-- the final state of the system is determined by the balance between these two opposite processes

When balancing an equation, what do you multiply and what do you add?

-You multiply the big number in front of the molecule by the small number next to the molecule. -You add the subscript numbers on one side of the equation. (like if Na is there twice on one side, you add those numbers)