Tuesday 28 January 2014

28.1.14 Answers to bond energy questions

Please let me know after you have checked your answers if there is a problem.

Grade C Question. 
Hydrogen burns in chlorine.
H2(g) + Cl2(g)          2HCl(g)
a. One each of H–H and Cl–Cl bonds breaks.
b.  Two H–Cl bonds form.
c.  Energy to break bonds = 434 kJ + 242 kJ = 676 kJ
  Energy given out on forming bonds
  = 2 × 431 kJ = 862 kJ
  Overall energy change = -186 kJ given out.

d. Exothermic

Grade A Question 3.
a.  Bonds broken = 1933kJ
  Bonds formed = 1959kJ
  Overall energy = -26kJ
b.  Exothermic as the value is negative
Grade B Question 4
a.Negative amount of energy given out. So products have less energy than the reactants.
b.Is the minimum energy needed to start a reaction.
Grade A  to A* Question 5
c.i. 3466kJ/mol
c.ii. -730 kJ/mol

Have fun








Sunday 26 January 2014

27.1.14 This week's homework

Please see the NEW science online homework site and work through at least TWO of the homeworks set for C7 module.


http://kerboodle.oxfordsecondary.co.uk/users/login.
For username and password and website please refer to the school website, science department, resources. It's at the end of the list.
Any problems see me asap and email as well.

Please complete for Monday  3rd Feb..

Wednesday 23 October 2013

Holiday homework

Due to many of you sitting Maths and English exams when we get back - a change of plan
C7 organic test is monday 25th nov , but the Rates of reaction homework is for monday 4th nov.