Acids and bases and reactions Flashcards
Properties of acids
-taste sour
-corrosive
-indicators to change colour
-can conduct electricity
Properties of bases
-taste bitter
-slippery
-corrosive
-react with acids=water
-can conduct electricity
Define indicator
Determine whether a solution is an acid or base
What was arrenhenius’s theory?
Acid dissociates in solutions to produce hydrogen ions
Bases ionise in solutions to produce hydroxide ions
Limitations to the theory
-substances may not have OH formula but can still form OH solutions
-rules on work in solutions in water
-reactions such as HCL+NH3–>NH4CL are unexplained
-not all salts are neutral
Define electrolytes
Liquids that can conduct an electric current
-must form ions to conduct when dissolving in water
Relationship between conc and electric current flow
greater conc of ion= bigger flow of electric current
Ionisation in acids (weak and strong)
strong: all acid molecules are fully ionised
weak: partially ionised
Ionisation in bases (weak and strong)
weak: partially dissociate or ionise
strong: fully ionise or dissociate
Define pH and it’s trends
Measure of a solutions acidity
-generally falls as hydrogen ions increase
-acidic solutions < pH 7
-base solutions > pH 7
-greater acidity = lower pH
-every change in pH = 10 fold change in H+
Types of reactions and their equations
- Neutralisation
acid + water –> salt + water - Acid and metal
acid + water –> salt + hydrogen gas - Acid and carbonate
acid + carbonate –> carbon dioxide + salt + water - Base reaction
acid + ammonium salt –> salt + ammonia + water
strongest acids
-hydrochloric acid
-hydrobromic acid
-chloric acid
-sulfuric acid
-nitric acid
-hydroiodic acid
What is instantaneous rate of reaction?
the change in concentration of an infinitely small time interval.
Define collision theory
For reactions to occur reactant molecules must collide:
-with sufficient activation energy to disrupt bonds
-correct orientation suitable for bond breaking
Define activated complex (look at example graphs)
-highest energy
-bond breaking/forming
-arrangement of atoms is unstable
-exists prior to reaction ending (instant)
What do successful collision depend upon?
-total number of collisions
-percentage of collisions which are successful
Relationship between reaction rate and nature of reactants
-involves bonding arrangement/breaking =likely to be slow at room temp
-no bond breaking = rapid at room temp
Relationship between conc and reaction rate
-conc increase = increase reaction rate
-increased conc= increase particles per unit volume available to collide
-more particles collide per unit time
-more collision therefore more successful collisions per unit of time
-increased reaction rate
Relationship between sub-division and reaction rate
Smaller pieces exposes more reactant to surface = surface area with smaller particles= larger SA
-cutting up increase sub division
-more reactant particles = exposed surface
-more collisions per unit time
-more collisions= more successful collisions per unit of time
-increase reaction rate
Relationship between temperature and reaction rate
-temp increases will increase the average kinetic energy of particles
-increases the number of particles with sufficient activation energy
-more particles with sufficient activation energy= increase proportion of successful collisions
-increase reaction rate
or
-increase Ek increases the speed of particle movement
-increase number of collision per unit time
-increase proportion of successful collision
-increase reaction rate
Relationship between catalyst and reaction rate
-reducing activation energy cause more particles to have sufficient energy
-increase in particles with sufficient energy = more successful collisions per unit of time
-increase reaction
Define catalyst
Substance providing an alternative reaction pathway with lower activation energy
-they are unchanged in reactions
Homogenous vs heterogenous catalysts
Homogenous
same physical state as reactants and products
Heterogenous
different physical state as reactants and products
3 types of catalysts
-enzymes
-metal nanoparticles
-catalytic converters
Define Enzymes
biological catalysts made from proteins
- 1 to 100 nanometres
How are metal nanoparticles catalysts?
-advantageous due to large SA to volume ratio
-more reactants can access catalyst
-more SA= increase collision due to available space
=increase in successful reactions
a small particle that ranges between 1 to 100 nanometres in size.
How are catalytic converters catalysts? (Car exhausts)
-convert CO and NO into non toxic CO2 and N2
-also convert unburnt hydrocarbons into CO2 and H20
-millions of tiny pores in honey comb shape provide a large SA
Random error is…
have measurement that are spread randomly above or below the true value
Systematic errors are…
errors have flaws in the method or apparatus that lead to results that are either always above or always below the true value
What is the collision theory
for reaction to occur
-molecules must collide with sufficient activation energy to disrupt bonds
-with correct orientation suitable for bond breaking
What is evident in an activated complex
-highest energy
-bond breaking/forming
-arrangement of atoms is unstable
-exists prior to instant reaction energy
