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51 Cards in this Set
- Front
- Back
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What is a Bronsted-Lowry acid? |
A proton donor- a substance that releases hydrogen ions in solution |
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What is a Bronsted-Lowry base? |
A proton acceptor |
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Define pH |
pH= - log [H+] |
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Define pOH |
pOH= -log [OH-] |
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pH + pOH = ? |
14 |
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What is Ka? |
The acid dissociation constant |
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Define pKa |
pKa = -log (Ka) |
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What is the expression for Kw? |
Kw = [OH-][H+] |
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What value is Kw at 298 kelvin? |
1 x 10^-14 |
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What happens to the pH of a strong acid when it is diluted by a factor of 10? |
The pH increases by 1 |
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What happens to the pH of a weak acid when it is diluted by a factor of 10? |
The pH increases by 0.5 |
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What is a buffer solution? |
A buffer solution is a solution that resists changes in pH when a small amount of acid or alkali is added |
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What is Le Chatelier's principle? |
If a factor affecting the position of the equilibrium is altered, the equilibrium will shift to oppose the change. |
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What is the relationship between pH and pKa? |
pH = pKa - log ([Acid]/[Base]) |
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What buffer is used in cells? |
Dihydrogen phosphate and Hydrogen phosphate
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What pH must blood be? |
7.4 |
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What buffer is used in blood? |
Carbonic acid going to either water and carbon dioxide or hydrogen ions and hydrogen carbonate ions |
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What happens as a result of pH change in food? |
It goes off |
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Give an example of a buffer used in food |
Sodium Citrate and Citric Acid |
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What is entropy? |
Entropy is a measure of disorder in a system |
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Which has higher entropy, solid or gas? |
Gas |
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Define Standard entropy |
The standard entropy of a substance is the entropy of one mole of a substance at 298k at 1atm of pressure |
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What are the units of entropy? |
J K^-1 mol^-1 |
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When is a reaction thermodynamically spontaneous? |
When the total entropy change is positive |
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What is a kinetically favourable reaction? |
A kinetically favourable reaction is one with an activation energy low enough such that it can proceed. |
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How do we calculate total entropy change? |
Total = System + Surroundings |
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How do we find the entropy change of the system? |
System = Products - Reactants |
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How do we find the entropy change of the surroundings? |
Surroundings = - Enthalpy change/Temperature |
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Define enthalpy change of solution |
The enthalpy change when 1 mole of a solute is dissolved in sufficient solvent such that further dilution causes no further enthalpy change, under standard conditions |
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Define enthalpy change of hydration |
The enthalpy change when 1 mole of aqueous ions is formed in solution |
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Define lattice enthalpy of formation |
The enthalpy change when 1 mole of a solid ionic compound is formed from gaseous ions. |
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How do you calculate the value of the rate constant, k? |
K = mol dm^-3 s^-1 / (Conc products) |
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What are the reactants and their roles in the iodine clock reaction? |
Hydrogen Peroxide: Reacts with KI Potassium Iodide: To produce Iodine Dilute Sulphuric acid: Catalyst Sodium Thiosulphate: To react with iodine Starch: To turn blue when iodine is present- ie when sodium thiosulphate has been used |
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Why can't the rate equation be determined from the stoichiometric equation for the reaction? |
Because the rate determining step may have a different equation to the stoichiometric equation for the reaction, and it is the reactants in the rate determining step that determines the rate equation |
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What is a heterogeneous catalyst? |
A heterogeneous catalyst is a catalyst in a different phase from the reactants
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What is a homogeneous catalyst? |
A homogeneous catalyst is one in the same state as reactants |
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What does a catalyst do? |
A catalyst increase the rate of reaction by providing an alternative reaction pathway with a lower activation energy |
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In a heterogeneously catalysed reaction between gasses, increasing the pressure will hardly increase the rate. Why? |
Because the reaction is heterogeneously catalysed, the catalyst is a liquid or gas. If the surface of the catalyst is already saturated, increasing the pressure won't increase this area. |
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What sorts of molecules absorb IR radiation? |
Molecules that change their dipole moment as they vibrate |
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What does microwave radiation do to molecules? |
Microwave radiation heats polar molecules by creating an electric field with which they align themselves. |
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What can UV radiation do to molecules? |
UV radiation can cause homolytic fission of bonds such as in Chlorine, starting free radical chain reactions. |
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What are the steps in answering a long question on NMR spectroscopy? |
1. State no. of proton environments 2. State no. of protons per environment (relative area) 3. Identify a group from shift data 4. Explain splitting pattern 5. Identify compound 6. Draw and match with peaks |
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How do you explain the splitting pattern in NMR spectroscopy? |
"The splitting pattern occurs such that the number of peaks is equal to the number of hydrogen atoms bonded to the adjacent carbon plus one, the n+1 rule" |
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What is the mobile phase in gas chromatography? |
An inert gas, such as nitrogen |
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What is the stationary phase in gas chromatography? |
A liquid coated on the inner coils |
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What is the term given to how long a substance spends in a chromatography machine? |
Retention time |
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What determines how quickly a substance moves through a chromatography column? |
How much it interacts with the stationary phase |
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What is the stationary phase of HPLC? |
Silica bonded to hydrocarbons- ie small solid particles tightly packed into the tube |
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What is the mobile phase of HPLC? |
A polar mixture like methanol and water |
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How is entropy change related to equilibria? |
Stotal = R lnK R is the gas constant K is Kp |
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What is the Arrhenius equation? |
k = Ae^(-Ea/RT) A = Arrhenius Constant e= e Ea = activation energy RT= Gas constant x Temperature k = rate constant |
