(a)(i) Sketch a graphical representation of Charles' law. (ii) Calculate the volume of oxygen that would be required for the complete combustion of 2.5 mole...
(a)(i) Sketch a graphical representation of Charles' law.
(ii) Calculate the volume of oxygen that would be required for the complete combustion of 2.5 moles of ethanol at s.t.p. [molar volume at s.t.p. = 22.4 dm\(^3\)]
(b)(i) State the collision theory of reaction rates.
(ii) Using the collision theory, explain briefly how temperature can affect the rate of a chemical reaction.
(c)(i) Define esterification.
(ii) Give two uses of alkanoates.
(iii) Give the products of the alkaline hydrolysis of ethyl ethanoate.
(d) A tin coated plate and a galvanized plate were exposed for the same length of time.
(i) Which of the two plates corrodes faster
(ii) Explain briefly your answer in 2(d)(i)
(a)(i) Graphical representation of Charles’ law
At constant pressure, the volume of a fixed mass of gas is directly proportional to its absolute temperature. A plot of volume against temperature in degrees Celsius is a straight line which, when extrapolated, cuts the temperature axis at 173 0C.
The straight line is extrapolated to zero volume at −273 °C (absolute zero).
Thus, \(V\propto T\) when \(T\) is measured in kelvin. A graph of \(V\) against temperature in kelvin passes through the origin.
(a)(ii)
The balanced equation for the combustion of ethanol is:
Volume of oxygen required = \(168.0\text{ dm}^3\) at s.t.p.
(b)(i) Collision theory states that a reaction occurs only when reacting particles collide effectively, that is, with energy equal to or greater than the activation energy and in the appropriate orientation.
(b)(ii) On raising the temperature, reacting particles gain kinetic energy and move faster. Collisions become more frequent and a greater proportion of the collisions possess at least the activation energy. The number of effective collisions per second therefore increases, so the reaction rate increases.
(c)(i) Esterification is the reaction of an alkanol with an alkanoic acid, usually in the presence of a concentrated mineral acid catalyst, to form an alkanoate and water.
(c)(ii) Alkanoates are used:
in perfumes and cosmetics;
as artificial food flavourings.
(c)(iii) Alkaline hydrolysis of ethyl ethanoate produces ethanol and a salt of ethanoic acid. For example, with sodium hydroxide:
(d)(ii) Tin is less reactive than iron, whereas zinc is more reactive than iron. If the coating is damaged, iron in contact with tin becomes the anode and corrodes rapidly. In a galvanized plate, zinc acts as a sacrificial metal and corrodes in preference to the iron, thereby protecting the iron plate.
At constant pressure, the volume of a fixed mass of gas is directly proportional to its absolute temperature. A plot of volume against temperature in degrees Celsius is a straight line which, when extrapolated, cuts the temperature axis at 173 0C.
The straight line is extrapolated to zero volume at −273 °C (absolute zero).
Thus, \(V\propto T\) when \(T\) is measured in kelvin. A graph of \(V\) against temperature in kelvin passes through the origin.
(a)(ii)
The balanced equation for the combustion of ethanol is:
Volume of oxygen required = \(168.0\text{ dm}^3\) at s.t.p.
(b)(i) Collision theory states that a reaction occurs only when reacting particles collide effectively, that is, with energy equal to or greater than the activation energy and in the appropriate orientation.
(b)(ii) On raising the temperature, reacting particles gain kinetic energy and move faster. Collisions become more frequent and a greater proportion of the collisions possess at least the activation energy. The number of effective collisions per second therefore increases, so the reaction rate increases.
(c)(i) Esterification is the reaction of an alkanol with an alkanoic acid, usually in the presence of a concentrated mineral acid catalyst, to form an alkanoate and water.
(c)(ii) Alkanoates are used:
in perfumes and cosmetics;
as artificial food flavourings.
(c)(iii) Alkaline hydrolysis of ethyl ethanoate produces ethanol and a salt of ethanoic acid. For example, with sodium hydroxide:
(d)(ii) Tin is less reactive than iron, whereas zinc is more reactive than iron. If the coating is damaged, iron in contact with tin becomes the anode and corrodes rapidly. In a galvanized plate, zinc acts as a sacrificial metal and corrodes in preference to the iron, thereby protecting the iron plate.
