OCR F334 The Thread of Life

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F334 Chemistry of Materials: The Thread of Life
Kinetics
(a) explain and use the terms:
Rate of reaction Rate of reaction the rate at which reactants are converted into products the change in
concentration of a reactant or product divided by the time taken for the change to occur.
Order of e.g. rate = k [H
2O 2] [catalase]
reaction (both The reaction is first order with respect to H
2O 2 and first order with respect to catalase. The
overall and with reaction is overall second order.
respect to a
+
given reagent) e.g. rate = k [BrO 3] [Br ] [H
]2
The reaction is first order with respect to both BrO 3 and Br , and second order with respect
+
to H .
If you double the concentration of the reactant and the rate stays the same zero order
with respect to the reactant.
If you double the concentration of the reactant and the rate doubles first order with
respect to the reactant.
If you double the concentration of the reactant and the rate quadruples second order
with respect to the reactant.
n
Rate of The general rate equation is: r ate = k[A]m [B] where m and n are the powers to which the
constant, concentration need to be raised they usually have the values of 0, 1 and 2. k is the rate
including units; constant the bigger it is, the faster the reaction. The value of k varies with temperature. m
use empirical + n gives the overall order of the reaction.
rate equations
of the form: Example: The reaction below was found to be second order with respect to NO and zero
3
rate = k[A]m n
[B] order with respect to CO and O 2. The rate is 1.76 x 10
mol dm3
s1 , when [NO] = [CO] = [O 2]
3 3
where m and n = 2.00 x 10 mol dm .
NO + CO + O2 NO 2 + CO
are integers; 2
carry out
1. Write out the rate equation :
calculations 0
Rate = k [NO]2 [CO]0 [O 2]
= k[NO]2
based on the 2. Insert the concentration and rate and rearrange the equation to give k:
rate equation 1.76 x 103
= k x (2.00 x 103
)2
3 3 2
k = 1.76 x 10 / (2.00 x 10 ) = 440
3. Find the units for k by putting the other units in the rate equation:
1 1 1
k = mol dm3 s / (mol dm3
)2 = s / mol dm3 = mol1 dm3 s
1 3 1
Therefore the answer is: k = 440 mol dm s
Overall Order Units for k
1
0 mol dm3 s
1 s1
1
2
mol1 dm3 s
2 6 1
3 mol dm s
Understand According to the rate equation, reaction rate depends only on the rate constant and
that the rate reactant concentrations . Since the reactant concentrations do not change, the rate
constant k constant must change. Therefore, the rate constant, k, increases with increasing
increases with temperature.
increasing
temperature

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F334 Chemistry of Materials: The Thread of Life
(b) understand that these experimental methods can be used in a school laboratory for following a reaction:
Titration Monitor the concentration of a reactant or product in a solution by taking small samples of
the reaction mixture at regular time intervals and titrating them. Add a large known
volume of distilled water to slow the reaction in the sample down.…read more

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F334 Chemistry of Materials: The Thread of Life
Ionic interactions between charged side groups, e.g. CO2
and NH3
+
.
Hydrogen bonding between groups such as OH and NH 2.
Disulfide bridge strong covalent bonds between two sulfurcontaining the side group SH.
Organic Reactions
(j) describe the acidbase properties of amino acids and recall that they usually exist as zwitterions
Amino acids are bifunctional compounds. They are unusual because the functional groups react.…read more

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F334 Chemistry of Materials: The Thread of Life
distance travelled by spot
Rf = distance travelled by solvent
(l) describe the characteristics of enzyme catalysis:
(m) explain these characteristics of enzyme catalysis in terms of a threedimensional active site (part of the
tertiary structure) to which the substrate forms intermolecular bonds, recalling that molecules acting as
inhibitors bind to active sites but no not react
Specificity Enzymes have a high specificity for a given substrate.…read more

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F334 Chemistry of Materials: The Thread of Life
Complementary base pairing allows replication to make new cells through cell division. One strand can make a
complementary copy of itself .
Complementary base pairing also allows protein synthesis. One strand can make a complementary copy of
messenger RNA , called transcription . The mRNA can then be translated into a chain of amino acids , called
translation.
Transcription Translation
Using enzymes, a section of DNA unwinds and unzips Protein synthesis takes place in ribsomes .…read more

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F334 Chemistry of Materials: The Thread of Life
A chiral carbon atom is one that has four different groups attached to it. It's possible to arrange the groups in two
different ways around the carbon atom so that two different molecules are made these molecules are called
enantiomers . Enantiomers are nonsuperimposable mirror images they can't be placed on top of one another
to give the same molecule.…read more

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