Sea water contains about 20gdm-³ of chloride ions, Cl-(aq). The exact concentration of Cl-(aq) in sea water can be determined by titration with aqueous silver ions, Ag+(aq), using aqueous potassium chromate(VI), K2CrO4(aq), as an indicator. When aqueous silver nitrate, AgNO3(aq), is added to a sample of sea water, silver ions react with chloride ions to form a precipitate of silver chloride. Ag+(aq) + Cl-(aq) → AgCl(s) When all of the Cl-(aq) has reacted with Ag+(aq), the presence of unreacted Ag+(aq) is detected by chromate(VI) ions, CrO42-(aq). A red precipitate of Ag2CrO4(s) is seen. 2Ag+(aq) + CrO42-(aq) → Ag2CrO4(s) The amount of Ag+(aq) reacting with Cl-(aq) in the sample of sea water can be calculated in order to determine the concentration of Cl-(aq) in the sample of sea water. A student uses the following method. step 1 Use a weighing boat to weigh by difference approximately 10.6g of AgNO3(s) into a 100 cm³ glass beaker. step 2 Use the sample of AgNO3(s) in the glass beaker to prepare 250.0 cm³ of AgNO3(aq). step 3 Transfer this solution into a dark brown glass bottle. Label this solution X. step 4 Collect a sample of sea water and remove any solid material present. step 5 Transfer 10.00cm³ of the sea water into a conical flask. step 6 Add 1 cm³ of K2CrO4(aq) to the conical flask. step 7 Rinse a burette in preparation for the titration. step 8 Fill the burette with solution X. step 9 Slowly add solution X to the conical flask until the white precipitate turns red. This is the end-point.