Chemistry Past Paper PDF

For assessment Hydrolysis- Is when any chemical reaction in which a molecule of water breaks one or more. For example when triacylglucerol splits into glycerol and three fatty acids. An acid or enzyme catalyst is required. Chemical bonds- bonds bw atoms to form molecules, Sulfide b...

For assessment Hydrolysis- Is when any chemical reaction in which a molecule of water breaks one or more. For example when triacylglucerol splits into glycerol and three fatty acids. An acid or enzyme catalyst is required. Chemical bonds- bonds bw atoms to form molecules, Sulfide bridge- Covalent bonds that links bw the sulphur atoms of two cysteine amino acids. Amino acid (essential)  Soap is made of- Can be made by 2 ways 1. Fat + oil 2. Strong base (NaOH) (hard) or (KOH) (liquid) + fat or oil  Polyhydric alcohols → How to identify it (copper reaction) Glycerol, titanic acid, glucose and other similar compounds have this property. The chelation reaction is demonstrated not only by its acidic properties but also by the presence of a diol moiety in the molecule. A method to identify polyhydric alcohols is their ability to react with copper (II) under specific conditions forming bright blue complexes or reducing copper (II) to copper (I) or copper metal. Arrehius definition (strong acids) → properties (differenciate bw soluble and insoluble) Arrhenius: Acts like a donor of protons. The acid in Arrhenius theory it dissociates to produce hydrogen ions (H+) in water. And a base in Arrhenius theory produces hydroxide ions (OH-) in water Bronsted- Lowry: Acts like a donor of protons. The acid is a proton donor and the base accepts protons. Lewis acids: Shares electrons. Accept electrons pair. Lewis bases: Shares elections. Donate electrons pair. Column chromatography- A preoperative technique used to purify compounds depending on their polarity or hydrophobicity. Carboxyl group + alcohol= ester This process is called esterfication and it typically occurs in the presence of an acid catalyst, such as concentrated sulfuric acid Strong acid with weak acid salts, what happens? Ans: 1. Displaces the weak acid and creates/ forms weak acid * buffer solution 2. Dissociates into ions When they react with eachother the strong acid displaces the weak acid from its salt. This reaction occurs because the strong acid has a higher tendency to donate protons (H+) compared to the weak acid Unsaturated fatty acids in oil? Unsaturated fatty acids in oil makes the fat more fluid at room temperautre compared to saturated fats. Fatty acid properties - What affect the absorption of conc, we length/ ex width, incident light flux The absorption of light by fatty acids, or compounds containing them, depends on their chemical properties and the conditions of the light source Calculation of pH, pOH, conc of H+ and OH– Calculations of pH: -lg[H3O+] Calculations of pOH: pOH= -lg[OH–] pH+pOH = 14.00 Calculations of [H3O+]: [H3O+]= 10–pH Examples calculations 1. In a solution [H3O+] = 0.01 M. What's the pH? Calculation: -lg[H3O+] = -lg[0.01]= 2 2. In a solution [OH–]= 0.01 M. What's the pH? Calculation: pOH= -lg[OH–]= -lg[0.01]= 2 pH- pOH= 2-14= 12 3. In a solution the pH= 4.68. Calculate [H3O+] Calculation: [H3O+]= 10–pH = 10–4.68 = 10–5 * 2.089296 mol/dm3 [H3O+]= 2.1 *10–5 mol/dm3 4. Calculate the pH in HCl where the concentration of HCl = 2.25* 10–5 M Calculation: pH= -lg[H3O+]= -lg[2.25*10–5]= 4.6478 pH in HCl= 4.678 Reactions in aldenydes (not in ketones) Aldehydes and ketones share similar functional groups (a carbonyl group, C=O), but aldehydes have a unique property: the carbonyl carbon is attached to at least one hydrogen atom, making aldehydes more reactive than ketones in certain chemical reactions. This difference allows aldehydes to undergo specific reactions that ketones typically do not. Phospholipids (head) → what makes it polar? Due to the phosphate group and the functional group. Peptide bond of amino acid Peptide bonds formation: - Amino acids link though a condensation reaction bw the carboxyl group of one and the amino group of another, forming a peptide bond. Basically, two amino acids are joined together to form protein. Tautomerism Is a type of isomerism in which two isomers, known as tautomers, readily interconvert by the migration of a proton (H+) and a shift in the position of a double bond. This equilibrium involves the redistribution of electrons, and the two forms exist in dynamic equilibrium. Keto-enol tautomerism- Is a chemical equilibrium bw to isomers which is a ketone (or aldehyde) form and its enol form (a compound with a double bond and a hydroxyl group attached to one of the doubly bonded carbons). This equilibrium occurs due to the migration of a hydrogen atom and the shifting of a double bond. The behavior of amino acid in acid or base solutions Amino acids are amphoteric molecules, meaning they can act as either acids or bases depending on the pH of the solution. The behavior of amino acids in acidic and basic solutions is largely determined by their amino group (-NH₂) and carboxyl group (-COOH). These two functional groups can ionize (gain or lose protons) depending on the surrounding pH, and the resulting ionic forms affect the amino acid's overall charge and solubility.