RATE OF A
CHRISTIAN CHARL O. COTORNO
Aim : To study the factors that affects the rate of a chemical reaction
Discussion : Although a balanced chemical equation for a reaction describes the
quantitative relationships between the amounts of reactants present and the amounts
of products that can be formed, it gives us no information about whether or how fast a
given reaction will occur. This information is obtained by studying the chemical
kinetics of a reaction, which depend on various factors: reactant concentrations,
temperature, physical states and surface areas of reactants, and solvent and catalyst
properties if either are present. By studying the kinetics of a reaction, chemists gain
insights into how to control reaction conditions to achieve a desired outcome.
Two substances cannot possibly react with each other unless their constituent
particles (molecules, atoms, or ions) come into contact. If there is no contact, the
reaction rate will be zero. Conversely, the more reactant particles that collide per unit
time, the more often a reaction between them can occur. Consequently, the reaction
rate usually increases as the concentration of the reactants increases.
A higher concentration of reactants leads to more effective collisions per unit time,
which leads to an increasing reaction rate (except for zero order reactions). Similarly, a
higher concentation of products tends to be associated with a lower reaction rate. Use
the partial pressure of reactants in a gaseous state as a measure of their
Usually, an increase in temperature is accompanied by an increase in the reaction
rate. Temperature is a measure of the kinetic energy of a system, so higher
temperature implies higher average kinetic energy of molecules and more collisions
per unit time. A general rule of thumb for most (not all) chemical reactions is that the
rate at which the reaction proceeds will approximately double for each 10°C increase
in temperature. Once the temperature reaches a certain point, some of the chemical
species may be altered (e.g., denaturing of proteins) and the chemical reaction will
slow or stop.
Part I : Effect of Concentration on Reaction Rate
The reaction of magnesium metal with hydrochloric acid solution of different
concentrations will be used to study the effect of concentration on reaction rate.
1. Using a 10-mL graduated cylinder,pour 5.0mL of each of the following
hydrochloric acid,HCI,solution into separate clean, dry test tubes: 0.1 M,1 M, 6 M.
2. Sandpaper three 1-cm strips of magnesium ribbon to remove the tarnish.
3. Drop a strip of magnesium ribbon into each of the test tubes.Note the time of
the reaction ends when bubbling ceases or no magnesium is left.Test for the gas
formed by holding a burning sprint near the mouth of each of the test tubes.A popping
sound indicates the presence of hydrogen gas.
4. Record your observations in the data table.
The test tube
is on going.
The test tube
is on going.
the test tube
and it produce
Hot Water 50
part of the test
tube is become
Part III: Effect of Catalyst on Reaction Rate
The decomposition of hydrogen peroxide into water and oxygen will be used
to study the effect of catalyst on the reaction rate.
1. Place 3.0 mL of 3% hydrogen peroxide, H2O2,measured with a 10-mL graduated
cylinder,into each of two clean,dry test tubes.
2. Put the two tubes in a test tube rack.
3. Add a pinch of manganese dioxide,MnO2,into one of the test tubes.Observe and
compare the rates of evolution of oxygen gas in the two tubes.
4. Record your observation in the data table.
Hydrogen peroxide is colorless and no
Hydrogen peroxide and manganese
It produce bubbles and when we start , it
becomes color black in the top and white
in the lower part and the recipitation is on
going.The coloris become black (charcoal)
Part IV : Effect of Particle Size and Surface Area on Reaction Rate
The reaction of iron with copper(II) nitrate,Cu(NO3)2 is used to investigate
the effect of particle size or surface area on reaction rate.
1.Weigh an iron nail,and put it in a clean,dry test tube.
2.Weigh an equal amount of powdered iron and put it in another test tube.
3.Put the two test tubes in the test tube rack. Add 3.0 mL of 0.1 M copper (II) nitrate,
Cu(NO3)2, to each tube.Observe and compare the rates at which the color of the
solution changes in the two tubes.
4.Record your observation in the data table.
The color of the iron nail is black and it
becomes bronze and the edge of the iron
nail is become color pink.
The color of the powdered iron is black
and when we put the CU(NO3)2 it is
become bronze and it produce tiny
1.Write a balanced equation for the reaction of magnesium metal with hydrochloric
2.Write a balanced equation for the decomposition of hydrogen peroxide.
3. Write a balanced equation for the reaction between iron and copper(II) nitrate.
4.Describe how reactant concentration, reaction temperature, catalyst, and the
surface area of liquid or solid reactant affect the rate of a chemical reaction.
5.Explain the difference in the rates of reaction of iron nail and powdered iron with
6. Explain why a miner is never permitted to smoke inside a coal mine?
7.Why does milk to remain unspoiled for two weeks when refrigerated but turns sour
when left at room temperature after a couple of days?
8.Why does a cold automobile battery may not generate enough energy to crank the
engine on a cold morning?Explain briefly.
1. Mg (s) +2 HCl (aq) yields MgCl2 + H2 (g)
Mg was oxidized sice it went from zero to +2.
H was reduced as it went from +1 to zero.
2. 2H2O2 = 2H20 + O2
4. The concentration of reactants plays an important role in chemical kinetics. It
is usually true that by increasing the amount of reactants, the rate of reaction is
increased. As we know that an increase in concentration of reactants increases the
number of molecules. According to collision theory, the greater the number of
molecules the higher is the collision ratio, consequently faster is the rate of reaction.
In heterogeneous reactions, the rate of reaction depends upon the surface area of solid
reactant. Greater the surface area, higher is the rate of reaction. For example finely
divided calcium carbonate (marble) reacts more quickly with hydrochloric acid than
calcium carbonate chips. It is due to the fact that powered calcium carbonate offers
larger surface area to the reacting acid. In other words, by increasing the surface area
of reactant, rate of reaction increases due to greater contact between individual
particles and also due to the fact that the surface molecules reacts more quickly.
The rate of reaction increases with the rise of temperature. It can be explain by the
fact that at higher temperature, a greater fraction of colliding molecules posse the
necessary energy of activation
Generally an increase of every 10oK in temperature doubles the rate.
As the temperature increases the velocity of molecules also increases which results in
the increase in the frequency of collision.
The rise in temperature rises the kinetic energy of each molecule. It has been found
that by raising the temperature by 10k,the fraction of molecule possessing threshold
or activation energy becomes double. As a result the no of effective collision is also
double,hence rate is doubled
5. Powdered Iron will react in a faster rate than a solid mass of iron. That's because
the higher surface area of powders. Means that's the total surface of Iron exposed to
Copper(II) Nitrate solution is much greater in case of the powdered form.
6. Miners break up coal from seams and that releases trapped combustible gas
(methane). Fires in coal mines then trap miners who smoked.
7. Milk has a large amount of bacteria in it. These bacteria can do various things, but
basically they eat and transform parts of the milk.
The bacteria go dormant (or die) at low temperatures, as well as high ones. This is why
boiling water is good if you don't have a proper water supply, because it will kill the
majority of the bacteria.
Room temperature is usually slightly below the ideal conditions for bacteria, but still
good. This will lead to the milk quickly spoiling. The cold refrigerator forces them to
8. the chemical fluid that makes the electricity to power the mechanical crank to start
the car is responsible.during the winter the cold slows down the chemical reaction so
it cant produce enough electricity to power the car.the opposite happens during the
summer , the heat makes the fluid accidentally react when it shouldn't and it then
leaks the electrical potential so when you actually go to your car it doesn't have