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topic 15 weaknesses
| Question | Answer |
|---|---|
| What does the reaction of acyl chloride and water produce? | Carboxylic acid and HCl. |
| What fumes are formed when acyl chloride reacts with water? | White misty fumes of HCl. |
| What is the reaction between acyl chloride and water like? | Vigorous. |
| What is NMR spectroscopy used for? | To determine the structure of a molecule by the magnetic field it produces. |
| Why can NMR only be used on atoms with an odd number of nucleons? | Only atoms with an odd number of nucleons have a nuclear spin needed to generate a magnetic field. |
| How do nuclei behave in a magnetic field? | They spin randomly but align with or against the external magnetic field. |
| What happens when radio waves are fired at aligned nuclei? | Electrons move up orbitals. |
| Why is energy released in NMR? | Electrons drop back to ground state, releasing radio waves. |
| What is the relationship between energy absorbed and released? | Energy absorbed = energy released. |
| What affects the amount of energy absorbed by atoms? | Bonding to a more polar atom causes less shielding and a higher value obtained. |
| Why is TMS used as a standard? | Contains 12 hydrogens in the same environment. |
| Why does TMS produce one peak far from sample peaks? | All hydrogens are identical and far from typical sample ranges. |
| What properties of TMS make it easy to use? | Inert, non-toxic, volatile. |
| What is one issue with NMR? | Peak values for certain substances can overlap. |
| What is another issue with NMR? | Peak values for a functional group may not show the whole group. |
| What is an optical isomer? | When a molecule has a chiral centre. |
| What is the slow step in SN1? | The first step where the C–halogen bond breaks heterolytically. |
| What is Tollens' reagent made of? | Silver nitrate and aqueous ammonia. |
| What is needed to make a carboxylic acid from a nitrile? | Water and HCl. |
| What is the waste product when converting nitrile to carboxylic acid? | NH4Cl |
| What conditions are needed when converting nitrile to carboxylic acid? | Heat under reflux. |
| What is the reduction equation for a carboxylic acid? | Carboxylic acid + 4[H] → primary alcohol + water. |
| What happens during halogenation of a carboxylic acid? | Halogen replaces OH. |
| What does halogenation of carboxylic acids form? | Acyl Halide. |
| Balanced equation for halogenation? | RCOOH + PCl₅ → RCOCl + POCl₃ + HCl. |
| What is the reaction of carboxylic acid and PCl5 like? | Vigorous |
| What reacts to form an ester? | Alcohol and carboxylic acid with sulfuric acid catalyst. |
| Is esterification fast or slow? | Slow and reversible. |
| How is water formed in esterification? | H from acid and OH from alcohol. |
| What forms when acyl chloride reacts with ammonia? | Primary amide and HCl. |
| What further product can form when acyl chloride reacts with ammonia? | NH4Cl |
| What forms when acyl chloride reacts with a primary amine? | N-methyl R-amide. |
| What is needed to hydrolyse an ester? | Water + dilute H₂SO₄ or dilute NaOH. |
| What reagents are used in acid hydrolysis? | Dilute H₂SO₄ or HCl. |
| What conditions are needed for acid hydrolysis of esters? | Heat under reflux. |
| What are the products in acid hydrolysis of esters? | Alcohol from section after O and carboxylic acid from section before O |
| What reagent is used in Base Hydrolysis? | Dilute NaOH. |
| What are the products of base hydrolysis of esters? | Carboxylate ion + alcohol (and metal ion). |
| What is saponification? | Base hydrolysis of esters to make soap |
| What is the stationary phase in TLC? | : Silica or alumina on glass/plastic. |
| What is the stationary phase in column chromatography? | Alumina or silica packed into a tube. |
| How does HPLC work? | Solvent forced into metal tube under high pressure. |
| What is special about HPLC stationary phase? | Smaller particle size gives better separation. |
| What detects components in HPLC? | UV absorbance. |
| What value is recorded instead of RF in HPLC? | Retention time. |
| What affects retention time? | Solvent Pressure Temperature inside column |
| What is the mobile phase in Gas Chromatography? | Inert gas. |
| What is the stationary phase in Gas Chromatography? | Solid or liquid coating inside tube. |
| How do components separate in Gas Chromatography? | Move at different speeds depending on attraction to stationary phase. |
| How is Mass Spectrometry used with chromatography? | Identifies separated components. |
| What extra advantage does HRMS give? | Mass to 4 d.p. (more accurate identification). |
| What are nucleons? | Protons and neutrons |
| What is chemical shift compared to in NMR? | TMS |
| What causes higher chemical shift in NMR? | Less shielding |
| Why may two atoms have the same chemical shift in NMR? | They are bonded to the same groups. |
| What is the chemical shift for TMS? | Zero. |
| Kw formula and value | [H+] x [OH-] = 1.0x10-14 |
| How do pKa values indicate acid strength | lower pKa = stronger acid pKa < 0 = strong pKa > 0 = weak |
| How is pH maintained when acid is added to acidic buffer? | Addition of H+ reacts with A- to make more acid and remove H+ |
| How is pH maintained when base is added to acidic buffer? | Addition of OH- reacts with HA to make H2O and A- to remove OH- |
| How is pH maintained when acid is added to basic buffer? | Addition of H+ reacts with base (B) to make BH+ and remove H+ ions |
| How is pH maintained when base is added to basic buffer? | Addition of OH- reacts with BH+ to make B + H2) and remove OH- ions |
| What is the Henderson - Hasselbalch equation? | pH = pKa + log [A-]/[HA] |
| Value of R? | 8.31 |
| Gibbs free energy equation (ΔG) | = ΔH - TΔS |
| What does Gibbs free energy show? | Whether a chemical reaction is spontaneous |
| Define lattice energy? | The energy released when one mole of an ionic compound is formed from gaseous ions. |
| What is covalent character? | When cation polarises anion. |
| What is enthalpy change of a solution? | The enthalpy change when 1 mole of a compound dissolves in water |
| What is enthalpy change of hydration? | the enthalpy change when one mole of gaseous ions are turned into one mol of aqueous ions |
| What increases entropy? | - increasing temp - increasing volume - increasing number of particles (mol/conc) |
| How many Ea does the energy profile for homogenous catalysts have? | 2 (or more) |
| What changes k in the rate equation | temperature and catalyst |
| how does unit of mol change when order of reaction increases | mol power decrease by 1 |
| how does units of dm change when order of reaction increases | dm power increases by 3 |
| how does units of s change when order of reaction increases | s power doesn't change from -1 |
| what are the units for a zero order reaction | moldm-3s-1 |
| what is the initial rates method | when experiment is repeated over and over until fixed amount of product formed/reactant used |
| what is a catalytic converter made of? | -made from rhodium, platinum and palladium alloy |
| What does a catalytic converter do | 2CO + 2NO --> 2CO2 + N2 |
| what is the arrhenius equation | k = A x e^(-Ea/RT) |
| what form of the arrhenius equation is used to plot graphs | lnK = -(Ea/R) x 1/T + lnA |
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