Chapter 9 Solutions
Opening Essay
If you watch any of the medical dramas on television, you may have heard a doctor (actually an actor) call for an intravenous solution of “Ringer’s lactate” (or “lactated Ringer’s”). So what is Ringer’s lactate?
Intravenous (IV) solutions are administered for two main reasons: (1) to introduce necessary substances into the bloodstream, such as ions for proper body function, sugar and other food substances for energy, or drugs to treat a medical condition, and (2) to increase the volume of the bloodstream.
One simple IV solution, called a normal saline solution, is simply a dilute solution of NaCl dissolved in water. Normal saline is 9.0 g of NaCl dissolved in each liter of solution. (The reason for this particular concentration is explained in Section 9.4 “Properties of Solutions”.)
Ringer’s lactate is a normal saline solution that also has small amounts of potassium and calcium ions mixed in. In addition, it contains about 2.5 g of lactate ions (C3H5O3−) per liter of solution. The liver metabolizes lactate ions into bicarbonate (HCO3−) ions, which help maintain the acid-base balance of blood. (Acids and bases are discussed in Chapter 10 “Acids and Bases”.) Many medical problems, such as heart attacks and shock, affect the acid-base balance of blood, and the presence of lactate in the IV solution eases problems caused by this imbalance.
Physicians can select from a range of pre-made IV solutions, in accordance with a patient’s particular needs. Ringer’s lactate is commonly used when a patient’s blood volume must be increased quickly. Another frequently used IV solution, called D5W, is a 5% solution of dextrose (a form of sugar) in water.
Solutions are all around us. Air, for example, is a solution. If you live near a lake, a river, or an ocean, that body of water is not pure H2O because other substances are dissolved in it. Many beverages such as coffee and tea are solutions. Solutions are a large part of everyday life.
Much of the chemistry that occurs in the human body takes place in solution, and many solutions—such as the Ringer’s lactate IV solution—are important for our health. In this chapter, you will learn about the special characteristics of solutions, how to express the concentration of a solution, and some properties of solutions.
