Reactivity Flashcards
(48 cards)
1
Q
Tartaric acid
A
Weak acid
2
Q
Ascorbic acid (vitamin c)
A
Weak acid
3
Q
H2CO3
A
carbonic acid, weak acid
4
Q
HCl
A
Hydrochloric acid, strong acid
5
Q
H2SO4
A
Sulfuric acid, strong acid
6
Q
HNO3
A
Nitric acid, strong acid
7
Q
Citric acid
A
Weak acid
8
Q
CH3COOH
A
Ethanoic acid, strong acid
9
Q
H2SO3
A
Sulfurous acid, weak acid (acid rain)
10
Q
Lactic acid
A
Weak acid
11
Q
HNO2
A
Nitrous acid, weak acid (acid rain)
12
Q
NaOH
A
Sodium hydroxide, strong base
13
Q
Ca(OH)2
A
Calcium hydroxide, strong base
14
Q
Mg(OH)2
A
Magnesium hydroxide, weak base
15
Q
NaHCO3
A
Sodium hydrogen carbonate, weak base
16
Q
CaCO3
A
Calcium carbonate, weak base
17
Q
Na2CO3
A
Sodium carbonate, weak base
18
Q
NH3
A
Ammonia, weak base
19
Q
Diprotic
A
Acids that can donate two hydrogen (H+) ions
20
Q
Monoprotic
A
Acids that can donate one H+ ion
21
Q
Amphiprotic
A
A substance that can act as either an acid or base. This means it can either lose a proton or gain one.
For example: Water (H2O) is amphiprotic, it can either form a hydroxide ion or a hydronium ion.
22
Q
Describe + explain the effects that adding a catalyst has on an equilibrium system
A
Kc remains constant.
A catalyst has no effect on the position of equilibrium, it does however enable the reaction to reach equilibrium faster by providing an alternative pathway requiring less activation energy (in both the forward and backward directions).
23
Q
Define a base
A
A substance that can accept hydrogen ions (H+) or donate hydroxide ions (OH-) when dissolved in water. Bases can neutralise acids, forming water and salt in the process.
24
Q
Define an acid
A
An acid is a substance that donates hydrogen ions (H+) when dissolved in water. This process increases the concentration of H+ ions in the solution.
25
Equilibrium
Equilibrium reactions do not go to completion. This means that at the "end" of the reaction there is always some products and reactants present in concentrations which will not change with time, but be maintained. Equilibrium reactions must be reversible, dynamic and closed. And these concentrations are continuously maintained so that the rate of reactants to products and vice versa are equal and consistent.
aA+bB ⇌ cC+dD
<----------- ---------->
(backwards, left) (forwards, right)
26
Strong acid
A strong acid is an acid that completely dissociates into its ions in water. This means that when a strong acid is dissolved in water, it releases all of its hydrogen ions (H+) into the solution, resulting in a high concentration of H+ ions.
27
weak acid
A weak acid is a substance that only partially dissociates (ionises) in water to produce H+ ions. This means that in a solution, only a small amount of the acid molecules release hydrogen ions (H+) while the majority of the acid remains in its molecular form. Weak acids have relatively low pH values and are used to neutralise strong bases.
28
Strong base
A strong base is a base that completely dissociates in water to release hydroxide ions (OH-). this means that when a strong base is dissolved in water, it fully separates into its constituent ions (breaks apart into its tiny building blocks, ions), resulting in a high concentration of OH- ions in the solution.
29
Weak base
A weak base is a substance that only partially dissociates (ionises) in water to produce OH- ions. This means that in a solution, only a small amount of the base molecules release hydroxide ions (OH-), while the majority of the base remains in its molecular formula.
30
Describe + explain the effects that changing pressure (only applicable to gas) has on an equilibrium system
Kc remains constant.
Increase in pressure (gases only):
The equilibrium system moves in the direction where there are fewer gas moles (less moles of gas mean less pressure).
Decrease in pressure (gases only):
The equilibrium system moves in the direction where there are more gas moles (more moles of gas mean more pressure).
Coefficient decides how many moles:
N2O4(g) ⇌ 2NO2(g)
31
What is a two-way reaction, in equilibrium?
A two-way reaction is a reversible reaction where the reactants can form products, and those products can also react to form the original reactants. This is shown by a double arrow (⇌), indicating that both the forward and reverse reactions are occurring.
A + B ⇌ C + D
In this reaction, A and B react to form C and D, and C and D can react to from A and B.
32
Describe + explain collision theory
In order for a reaction to occur:
- the reactant particles must collide.
- the collision must be effective.
For a collision to be effective the particles must collide:
- With the correct orientation
- with sufficient energy to overcome the activation energy barrier.
Reactant particles energetic & orientated correctly = chemical reaction
if conditions are changed to allow more frequent effective collisions to occur, then the overall reaction rate will increase.
33
Describe and explain the effects that changing concentrations have on an equilibrium system
Kc remains constant
>Addition of a reactant OR removal of a product: The equilibrium system moves in the forward direction (right) producing more products to use up some of the added reactant/product removed.
*The queue moves forward because someone has stepped out.
>Removal of a reactant OR addition of a product: The equilibrium system moves in the backward direction (left) producing more reactant to replace some of the reactant removed/product added.
*The queue moves backward because someone has cut in.
34
Describe + explain the effects that changing temperature has on an equilibrium system.
Kc changes
Increase in temperature: The reactions moves in the endothermic (H +ve) direction to use up (absorb) the added heat. Kc is altered.
Heat + reactant ==> products
Decrease in temperature: The reaction moves in the exothermic (H -ve) direction to produce more heat (to reheat the system).
Reactants ==> products + heat
34
Describe + explain the effect of adding a catalyst on the reaction rate.
A catalyst is a substance that participates in but is not used up by a reaction and has the effect of increasing the rate of reaction. The catalyst achieves this by providing an alternative pathway that has a lower activation energy requirement than normal. This lower energy requirement means that more particles will collide with sufficient energy to enable a successful reaction. Thus, the effectiveness of collisions has been increased.
35
State 'Le Chateliers principle'
When a system in equilibrium is subjected to a change, the
equilibrium will shift to counteract that change, and restore a new equilibrium.
i.e. If a chemical reaction is at equilibrium and experiences a change in pressure, temperature, or concentration of products or reactants, the equilibrium shifts in the opposite direction to offset the change.
When equilibrium shifts we state the side that is favoured by using specific terms:
- products are favoured
- reactants are favoured
- moves (shifts) in a backward direction
- moves (shifts) in a forward direction
35
Describe + explain activation energy
Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is the energy barrier that reactants must overcome to be transformed into products. When molecules collide with enough energy (equal to or greater than the activation energy), they can successfully react to form products. If they collide with less energy, they wont react and will just bounce off each other. Higher activation energy means a slower reaction rate because fewer molecules have enough energy to react. In diagrams, activation energy is represented as the peak of an energy curve, where the reactants must reach the peak before forming products.
36
Describe + explain the effect that surface area has on a reaction rate
- The surface area of a solid reactant can be increased by crushing or powdering a big lump into many smaller pieces.
- This means there are more solid reactant particles exposed for collisions with another reactant, and this greater frequency of collisions result in a greater rate of reaction.
- Dissolving a solid reactant, effectively increases its surface area available for collisions to the maximum, because the dissolving process separates solids into individual particles.
37
Describe + explain the effect that changing concentration has on a reaction rate
When the concentration of a reactant is increased, the frequency of collisions increases as there are more particles available for collisions. Therefore, the rate of reaction increases. If gases are involved changing the pressure or volume of the container will change the effective concentration of the substance.
NOTE: The rate of all chemical reactions decreases as the reaction proceeds, because as the reactants are used up, their concentration decreases and therefore slows the rate. Increasing the number of collisions does not increase the rate of reaction.
37
Kw
38
Describe + explain the effect of temperature changing has on a reaction rate.
If the temperature is increased the average kinetic energy of the particles also increases which increases the ROR for two reasons:
a) As the particles move faster, they will collide more often with other particles, so the collision frequency increases.
b) More importantly, as the average kinetic energy of the particles increases, a larger proportion of the collisions will have sufficient energy to successfully overcome the activation energy barrier. i.e. there is an increased frequency of effective collisions (those whose energy exceeds the activation energy).
39
Calculating the hydroxide ion concentration from pOH
39
Calculating the hydronium ion concentration from pH
40
Relationship between pH and pOH
41
Calculating pOH
pOH = -log [OH-]
42
Calculating pH
43
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