Write the equations relating DG and K to the standard emf of a cell. Define all the terms
The bigger Ka is, the stronger the acid is, and the less basic that its anion is. For all strong acids, the anion is neutral, but for weak acids, the anion is basic. Ex. Perchlorate and sulfate are neutral anions, but fluoride and cyanide are basic anions. If a salt contains a basic anion, the salt will form a basic solution when dissolved in water. Ex. Sodium acetate, potassium fluoride. Useful equations for pH problems: −¿ OH ¿ ¿ ¿ +¿ H ¿ ¿ ¿ pKa+pKb=14 Sample problem: You have a solution of 0.1 M HCl and 0.1 M HF. Calculate the pH. The HCl will dissociate completely, so that the concentration of the free hydrogen ions will be equal to the HCl concentration. The HF does not dissociate completely. It dissociates according to the following equation: + - HF H + F According to Le Chatelier’s Principle, addition of an ion to one side of the equation will push the reaction to the other side. The additional H caused by the dissociation of HCl will make HF even less likely to dissociate. Thus, the weak acid can be ignored in the calculation of the pH; only the concentration of the strong acid is needed. Take the negative logarithm of the concentration of the strong acid to find the pH. Acidic salts are the result of the neutralization of a strong acid and a weak base. Acidic salts can also result when the salt contains small, highly charged ions, like aluminum. The easier the free hydrogen atom is to remove, the stronger the acid. For a binary (two-atom) acid, strength increases down a column (HI is stronger than HBr which is stronger than HCl which is stronger than HF). The bigger atoms have more electron shells between themselves and the hydrogen proton; therefore, they do not attract it as strongly. For oxoacids (acids containing oxygen atoms), acid strength increases as the number of oxygen atoms involved increases. Acid strength also increases as the non-oxygen non-hydrogen atom increases in electronegativity. HClO is stronger than HBrO which is stronger than HIO. For polyprotic acids, acid strength decreases as the acid loses protons.