C7, C8 Flashcards
bond making is:
exothermic
the effect of pressure
- increasing the pressure increases the frequency of collisions
- so increases the rate of reaction
collision theory:
- particles collide all the time, but only some lead to reactions
- increasing the number of collisions produces faster rates of reactions
- larger surface area increases the frequency of collisions.
reaction profile for exothermic reactions:
-the products are at a lower energy level than the reactants.
energy and reversible reactions
- one reaction is exothermic and the other is endothermic
- the amount of energy transferred to the surroundings in one direction is exactly equal to the the energy transferred back in the other direction
energy is conserved in chemical reactions. It is neither created nor destroyed
energy is conserved in chemical reactions. It is neither created nor destroyed
endothermic reaction examples:
- citric acid and sodium hydrogencarbonate
- decomposition of calcium carbonate
surface area:
- if the surface area to volume ratio of any solid reactants increases the rate of a reaction increases.
- this increases the frequency of collisions between reacting particles
how can you represent reversible reactions?
-using the sign with one arrow pointing forwards and one pointing backwards.
reaction profile for endothermic reactions:
-the products are at a higher energy level than the reactants.
exothermic changes use:
- hand warmers
- self-hearing cans
explain the experiment for hydrochloric acid(required practical)
place 1 g of marble chips(calcium carbonate) in a chronicle flask of 50 cm³ of hydrochloric acid. Immediately placed the bung on the chronicle flask and record the…
what happens when the pressure is decreased in a reversible reaction? (le chatelier’s principle)
when pressure is decreased, volume is increased and makes a shift to the left with more moles of gas
the activation energy is:
the minimum amount of energy needed to start a reaction
what happens if we remove the heat from the reversible reaction? (le chatelier’s principle)
if heat is removed we shift to the right
the effect of temperature:
- as temperature increases reactions happen more quickly
- increasing temp increases the rate of reaction because particles collide more frequently and more energetically
dynamic equilibrium
- in a closed system, the rate of the forward and reverse reactions is equal at equilibrium.
- changing reaction conditions can change the amount of products and reactants in a reaction mixture at equilibrium
catalyst examples
- iron to make ammonia
- platinum to make nitric acid
define equilibrium
the state in which both reactants and products are present in concentrations which have no further tendency to change with time
what is a reaction in which energy is transferred to the reacting substance from their surroundings called?
endothermic
what is a reversible reaction?
-a reaction where the products can react to make the original reactants
main factors which affect the rate of chemical reactions:
- temperature
- surface area of solids
- concentration of solutions or pressure of gases
- presence of a catalyst
altering conditions (pressure)
- increasing the pressure favours the reaction that forms fewer molecules of gas.
- decreasing the pressure favours the reaction that forms the greater number of molecules of gas
(changing pressure affects the equilibrium only if there are different numbers of molecules of gases on each side of the balanced equation)
what happens when nitrogen or hydrogen is added to the reversible reaction? (le chatelier’s principle)
if you add nitrogen or hydrogen the equilibrium shifts to the right or towards the products
