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Flashcards in C5 - energy changes Deck (17)
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1

Define an exothermic reaction

Energy is given out to the surroundings because more energy was given out by making bonds than was taken in for breaking bonds

2

Does an exothermic reaction get warmer or colder?

warmer

3

define an endothermic reaction

Energy is taken in from the surroundings because more energy was taken in for breaking bonds than was given out by breaking bonds

4

does an endothermic reaction get warmer or colder?

colder

5

Give two examples of an exothermic reaction

combustion, neutralization reactions

6

Give two examples of endothermic reactions

the reaction between citric acid and sodium hydrogencarbonate, thermal decomposition (photosynthesis also counts but it isn't in the book)

7

give two uses of exothermic reactions

some hand warmers and self-heating cans

8

give a use of endothermic reactions

some sports injury packs

9

what are reaction profiles?

diagrams that show the relative energies of the reactants and products in a reaction, and how the energy changes over the course of the reaction

10

If the reactants are higher than the products in a reaction profile, is the reaction exothermic or endothermic?

exothermic

11

if the reactants are lower than the products in a reaction profile, is the reaction exothermic or endothermic?

endothermic

12

what is the name of the initial rise of energy in a reaction profile?

activation energy

13

what is activation energy?

the minimum amount of energy the reactants need to collide with each other and react. The greater the activation energy, the more energy needed to start the reaction.

14

what does the overall difference in height of a reaction profile represent?

the overall energy change during the reaction

15

Does breaking bonds require energy or release energy? Is it exothermic or endothermic?

It requires energy - it is endothermic

16

does forming bonds require energy or release energy? is it exothermic or endothermic?

It releases energy - it is exothermic

17

H-H: +436 kJ/mol; Cl-Cl; + 242 kJ/mol; H-Cl: +431kJ/mol
work out the total energy change for the reaction H2 + Cl2 -> 2HCl

-184 kJ/mol