Chemistry_Grade_10-12 (1).pdf

H 2 k c a increases increases b increases unchanged c

Info icon This preview shows pages 327–330. Sign up to view the full content.

View Full Document Right Arrow Icon
[H 2 ] K c A increases increases B increases unchanged C unchanged unchanged D decreases unchanged 313
Image of page 327

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
16.8 CHAPTER 16. REACTION RATES - GRADE 12 (IEB Paper 2, 2004) 3. During a classroom experiment copper metal reacts with concentrated nitric acid to produce NO 2 gas, which is collected in a gas syringe. When enough gas has collected in the syringe, the delivery tube is clamped so that no gas can escape. The brown NO 2 gas collected reaches an equilibrium with colourless N 2 O 4 gas as represented by the following equation: 2 NO 2 ( g ) N 2 O 4 ( g ) Once this equilibrium has been established, there are 0.01 moles of NO 2 gas and 0.03 moles of N 2 O 4 gas present in the syringe. (a) A learner, noticing that the colour of the gas mixture in the syringe is no longer changing, comments that all chemical reactions in the syringe must have stopped. Is this assumption correct? Explain. (b) The gas in the syringe is cooled. The volume of the gas is kept constant during the cooling process. Will the gas be lighter or darker at the lower temperature? Explain your answer. (c) The volume of the syringe is now reduced to 75 cm 3 by pushing the plunger in and holding it in the new position. There are 0.032 moles of N 2 O 4 gas present once the equilibrium has been re-established at the reduced volume (75 cm 3 ). Calculate the value of the equilibrium constant for this equilibrium. (IEB Paper 2, 2004) 4. Consider the following reaction, which takes place in a closed container: A(s) + B(g) AB(g) Δ H < 0 If you wanted to increase the rate of the reaction, which of the following would you do? (a) decrease the concentration of B (b) decrease the temperature of A (c) grind A into a fine powder (d) decrease the pressure (IEB Paper 2, 2002) 5. Gases X and Y are pumped into a 2 dm 3 container. When the container is sealed, 4 moles of gas X and 4 moles of gas Y are present. The following equilibrium is established: 2X(g) + 3Y(g) X 2 Y 3 The graph below shows the number of moles of gas X and gas X 2 Y 3 that are present from the time the container is sealed. 30 time (s) 0,5 4 number 70 100 moles of 314
Image of page 328
CHAPTER 16. REACTION RATES - GRADE 12 16.9 (a) How many moles of gas X 2 Y 3 are formed by the time the reaction reaches equilibrium at 30 seconds? (b) Calculate the value of the equilibrium constant at t = 50 s. (c) At 70 s the temperature is increased. Is the forward reaction endothermic or exothermic? Explain in terms of Le Chatelier’s Principle. (d) How will this increase in temperature affect the value of the equilibrium constant? 16.9 Industrial applications The Haber process is a good example of an industrial process which uses the equilibrium principles that have been discussed. The equation for the process is as follows: N 2 ( g ) + 3 H 2 ( g ) 2 NH 3 ( g ) + energy Since the reaction is exothermic , the forward reaction is favoured at low temperatures, and the reverse reaction at high temperatures. If the purpose of the Haber process is to produce ammonia, then the temperature must be maintained at a level that is low enough to ensure that the reaction continues in the forward direction.
Image of page 329

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 330
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern