Supplementary Material - Ch3 Basic Concepts in Chemistry PDF

Biology 1002130 Supplementary material – Ch3 M1 to Liter we - by 1000 Dr. Noor Al-Saigh and Dr. Amani Alhadid 27.oct. 2024  Molarity...

Biology 1002130 Supplementary material – Ch3 M1 to Liter we - by 1000 Dr. Noor Al-Saigh and Dr. Amani Alhadid 27.oct. 2024  Molarity # of mol o Molarity is an expression of concentration. - Molarity = no. of moles of solute / Volume of solution in liters. M = 1 of volume M = ) - Expressed as molar (M) or mol / L. mass(g) o No. of moles = mass (g) / molar mass (g/mole). mol = M. m (y/more) from periodic table o One mole of a substance is equal to 6.022 × 10²³ units of that substance (such as atoms, molecules, or ions). The number 6.022 × 10²³ is known as Avogadro's number o The molar mass of a substance is the mass of one mole of that substance. - Expressed in g/mol or Dalton. molar concentration is Molarity - Dalton (Da) = 1/12 mass of 12C. - Numerically, Dalton is equivalent to g/mol. []: Molar concentration = #mols / L Example: volume Meme Find the molarity of 0.3 Kg NaCl dissolved in 700 ml water. Answer: M = # of - L of mol volume #otmol= as zom = 0. 7- volume # of mol = 20 4y (from table) · periodic M 300 y = mol 5 1 Molarity = no. of moles / Solution volume (L). # of = mass 1000 =. M = 7 3. 0. 3kg X No. of moles = mass / molar mass. (Molar mass of NaCl = 58.44 g/mol). 0.3 Kg = 300 g. 700 ml = 0.7 L. 158 44) = Na the period table ·.. >>> molarity = (300 g ÷ 58.44 g/mol) /0.7 L = 7.33 M (or 7.33 mol / L). = >  Types of Chemical Bonds: 1  The major functional groups in chemistry:  Hydroxyl group  Carbonyl group  Carboxyl group  Amino group  Sulfhydryl group  Phosphate group  Methyl group ? 2 an 2  Acids & Bases: - Acid: is a proton donor. Acid: H+ donor - Base: is a proton acceptor. Base: H+ acceptor + + - pH: is a measure of the concentration of H [H3O ] ions in a solution. (H+: Proton) +] pH= -log [H pH is a measure of acidity: ↑[H+] →↑ acidity → ↓pH pH is a measure of the concentration of H+ [H3O+] ions in a solution. - Buffer: is a solution that can resist change in pH. Only the concentration of H+ and Buffers can resist change in pH when adding small amounts OH- molecules determine the pH. [H+ ]= [OH- ], the solution is neutral. of acids or bases. [H+ ] > [OH- ], the solution is acidic The buffer is composed of either: [OH- ] > [H+], the solution is basic. A weak acid + its conjugate base (HA + H2O↔ H++ A-) OR => => A weak base + its conjugate acid (A + H2O↔ AH++ OH-) - pH= -log [H+] o Examples: Acid pH is a measure of acidity: CH3COOH + H2O↔ CH3COO- + H+ Acid ↑[H+] →↑ acidity → ↓pH 1. Ammonia and ammonium: Base pH is inversely proportional with NH3 + H2O↔ NH4+ + OH- Base log [H+], which means that small changes in pH means BIG To make a buffer, the conjugate acid or base are added as a salt changes in acidity. (e.g. CH3COONa "sodium acetate"). Each 1 unit change of pH is Buffer salt equivalent to 10 folds change in  The Dissociation constant of weak acids (Ka): [H+] (e.g., if pH decreased from 3 to 2, this means that [H+] has HA + H2O↔ H++ A- increased by 10 times). [ ] [ ][ ] Ka= = * [ ] [ ] pKa= - log Ka Weak acid: Partial pKa indicates the extent of dissociation. dissociation. ↓Ka → ↓dissociation →↑pKa → The weaker the acid, and vice versa. e.g.: Acetic acid Thus, only weak acids have pKa, strong acids have no pKa. (CH3COOH), Phosphoric acid (H3PO4) Strong acid: Full dissociation. e.g.: Hydrochloric acid (HCl), Sulfuric acid (H2SO4) 3 Acids can be either: * - Monoprotic: with one proton to lose, e.g.: HCl, CH3COOH OR - Polyprotic: with more than one proton to lose, e.g.: H2SO4, H3PO4. Polyprotic acids have >1 pKa (one for each proton).  Buffering capacity: Buffers can resist changes in pH only within a certain range = pKa ±1. Maximum Buffering capacity: when pH=pKa. (e.g.: pKa of acetic acid buffer = 4.8 → the buffering range= 3.8 – 5.8, the maximum buffering capacity is at pH = 4.8).  Handerson- Hasselbalch equation: [ ] pH= pKa + log [ ] Used to calculate the pH of a buffer or the concentration of its components, and to calculate the pI of proteins. How do buffers work? Buffers resist big changes in pH upon adding limited amounts of acids or bases: - When adding an acid (H+): the concentration of H+ increases, so the equilibrium is shifted to the left forming HA. HA does not affect pH since the H is not free. - When adding a base (OH-): OH- reacts with H+ forming water. Water is neutral → no big change on pH. [H+]↑→Equilibrium is shifted to the left OH- reacts with H+ forming water + - forming more HA→ no big change on [H+] (pH) H OH (NEUTRAL)→ no big change on pH. (pH). HA + H2O ↔ H+ + A- The three primary major buffering systems in the body are: Carbonic acid-bicarbonate buffer - Phosphate buffer system - Protein buffer system. Look it up! How does each one of those systems act as a buffer in the body? 4