Legal. One reason might be that titrations can be good for studying newly discovered molecules, for instance to measure the molecular weight and other properties that we will study more later. Copper sulphate (CuSO4). suggest that titrations are still very important in industry. Heat capacities to low temperatures. For instance, you might add a standard base solution to an mystery acid solution. The basic process involves adding a standard solution of one reagent to a known amount of the unknown solution of a different reagent. Thus, we must standardize the solution to precisely determine the final concentration. Solid NaOH is very hygroscopic, that is it absorbs water from the air, so it is very hard to weigh exactly. Then we add NaOH slowly until the indicator color changes. Watch the recordings here on Youtube! Examples of Hygroscopic Materials . Similarity in this cycle water is the refrigerant and the hygroscopic compound the absorbent. You also add an indicator, which is a molecule that changes color when the original reagent (the acid in the mystery solution, say) is completely consumed by reaction with the standard solution reagent. NaOH is insoluble in ether and other non-polar solvents. First we calculate the moles of HCl in the whole "2.5 M" solution, which is equal to the number of moles of HCl in quantity of stock solution ("10 M") that was used to make it (250ml). We calculate the number of moles of NaOH added: \[(5.1079\; mol/L)(46.67\; mL)= 238.4\; mmol\]. Spencer Umfreville Pickering (1893): "LXI.—The hydrates of sodium, potassium, and lithium hydroxides". (We made this solution in the previous section on molarity.) Germinating seeds are hygroscopic. Then you add the standard solution in a buret, which is a special tube for adding solution slowly and measuring the volume added at the end. We have a solution of HCl whose concentration is known imprecisely (~2.5 M). Titrations might seem a little old-fashioned. Sodium hydroxide (NaOH). It can absorb so much water that it actually dissolves. The overall reaction is CO 2 (g) + 2 NaOH (aq) Na 2 CO 3 + H 2 O This decreases the concentration of the OH-ions in the solution. We want to determine the concentration more precisely. Emily V Eames (City College of San Francisco). Pure sodium hydroxide is a colorless crystalline solid that melts at 318 °C (604 °F) without decomposition, and with a boiling point of 1,388 °C (2,530 °F). Missed the LibreFest? Once titrated, you could dilute it precisely to the concentration you want. The English chemist and archaeologist Henry Ernest Stapleton (1878–1962) presented evidence that the Persian alchemist and physician, Stapleton, H. E. and Azo, R. F. (1905) "Alchemical equipment in the eleventh century, A.D.,", O'Brien, Thomas F.; Bommaraju, Tilak V. and Hine, Fumio (2005), dissolving amphoteric metals and compounds, process for mass-producing sodium carbonate, "Sortierte Liste: pKb-Werte, nach Ordnungszahl sortiert. I know that sodium hydroxide is hygroscopic, but why not magnesium hydroxide (at least to the same extent as $\ce{NaOH}$)? For this reason, even if you buy it dry, once you open the bottle, it might start to absorb water, and it would be difficult to know when you measure it what % water it is. Have questions or comments? Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. For this reason, even if you buy it dry, once you open the bottle, it might start to absorb water, and it would be difficult to know when you measure it what % water it is. Many of the standard reagents you might use in the lab, especially HCl and NaOH, which are very common and important, are hard to prepare at precise concentration without titration. It can absorb so much water that it actually dissolves. Silica gel. To determine this, you would use a standard solution made of some easier-to-mass acid or base to titrate the solution you actually want to use. As the addition takes place, the two reagents in the solutions, in this the acid and base, react. Now, we diluted 250 mL of the original stock solution to 1.00 L to make this solution. Lye-water is an essential ingredient in the crust of the traditional baked Chinese moon cakes. NaOH can be purchased as a solid, but it is hygroscopic which means that it absorbs water from the air. – Das Periodensystem online", National Institute for Occupational Safety and Health, "ChemIDplus – 1310-73-2 – HEMHJVSKTPXQMS-UHFFFAOYSA-M – Sodium hydroxide [NF] – Similar structures search, synonyms, formulas, resource links, and other chemical information. Now you know exactly how much standard was added! Thus, if you work in a biochemistry lab, for instance, you might want to control the pH of your solutions by adding a little bit of dilute HCl or NaOH, because chloride and sodium ions are very common and probably are already included in the solution, but you might want to know how concentrated your solutions are.