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IGCSE化学反应能量介绍

INTERNATIONAL SCHOOL INFORMATION

  IGCSE是目前国外14岁至16岁全世界最多人读的体系,是CIE(Cambrige International examination)剑桥全球测试的一部分。

Energy change in chemical reactions

Activation energy Heat of reaction energy (kJ)

Progress of reaction

• Methane burns in oxygen: • CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) • Calculate the enthalpy change for this reaction using the following bond enthalpies / kJ mol-1: • C-H in methane = +435; O=O in oxygen = + 498; C=O in carbon dioxide = + 805; H-O in water = + 464

Bonds broken Bonds made

ΔH =Learning check

• A common means of forming small quantities of oxygen gas in the laboratory used to be to heat KClO3: • 2KClO3(s)→2KCl(s)+3O2(g) △H=-89.4kJ • For this reaction, calculate △H for the formation of • (a) 0.715mol of O2; • (b) 6.14g KCl;

Factors affecting the rate of reaction

• The surface area of any solid reactants • The concentration of the reactants • The temperature at which the reaction is carried out • The use of catalysts • The influence of light on some reactions.

Surface catalysts and collision theory

• Solid catalysts • One broad group of catalysts works by adsorbing molecules onto a solid surface.

• A catalyst increase the rate of reaction by reducing the amount of energy that it need to break the bonds.

Enthalpy, H (kJmol-1) Ea Ea(cat) reactants uncatalysted reaction

catalysted reaction

△H

products

Reaction pathway

The catalysed reaction follows a different route with a lower action energy .

Photochemical reactions

• Photosynthesis traps energy when sunlight falls on leaves containing the green pigment chlorophyll. • 6CO2+ 6H2O→C6H12O6 + 6O2

  目前中国鲜有人知道IGCSE,大部分人知道的是SAT,因为SAT是进美国大学必不可少的。但是想进英系大学,如剑桥,牛津大学的人应关心一下。

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