Why is salt a solute

When discussing solutions, we typically talk about the solution's concentration. In chemistry, we use molarity to calculate the concentration.

Other important terms are the molality and mole fraction of a solution. The molarity is the number of moles of solute per liter of solution. This is a specific concentration measurement. Molarity is defined as the number of moles of solute per unit volume. Molarity is temperature dependent as the volume of the density of a solution typically changes with temperature. The molality is the number of moles of solute per kilogram of solvent.

This measurement is not temperature dependent, as the mass does not change with temperature. A mole fraction , as the name implies, is a comparison of the number of moles in solution.

Since this is a fraction, there are no units. The mole fractions of a solution must add up to one. Let's look at a simple solution made of two components, 1 and 2. X is the mole fraction and n is the number of moles.

A solution is prepared by dissolving Calculate the molarity, molality and mole fraction of MgCl 2 if the density of water is 1. For the solution in Example 1, Now remember what is happening. Mole Fraction: Again we will start with the mole fraction. To determine this, the number of moles of Cl - is needed. We already calculated the number of moles of water in Example 1, However, the mole fraction is the number of moles for Cl - divided by the total number of moles of all species in the solution.

Now the mole fraction is calculated by: Molarity: For the molarity, the number of moles of solute per liter of solution is needed. In salt solution, salt is the solute. A solvent is the substance that does the dissolving — it dissolves the solute.

In salt solution, water is the solvent. During dissolving, particles of solvent collide with particles of solute. Model how water dissolves salt Look at the pictures showing how water molecules dissolve salt.

Move the water molecules and sodium and chloride ions to model how water dissolves salt. Tape the molecules and ions to the paper to represent water dissolving salt. Explore Have students conduct an experiment to find out whether water or isopropyl alcohol would be better at dissolving salt. Ask students to make a prediction: Think about the polarity of water molecules and alcohol molecules. Do you think alcohol would be just as good, better, or worse than water at dissolving salt?

Be sure students identify variables such as: Amount of water and alcohol used Amount of salt added to each liquid Temperature of each liquid Amount of stirring Question to Investigate Is alcohol just as good, better, or worse than water at dissolving salt? Place 15 mL of water and alcohol into separate cups. At the same time, add the water and alcohol to the samples of salt. Swirl both cups the same way for about 20 seconds and check for the amount of salt dissolved.

Swirl for another 20 seconds and check. Swirl for the last 20 seconds and check. Carefully pour off the water and alcohol from the cups and compare the amount of undissolved salt left in each cup.

Expected Results There will be less undissolved salt in the cup with the water than the alcohol. Explain Discuss how differences in the polarity of alcohol and water explain why water dissolves salt better than alcohol.

Ask students: Is alcohol just as good, better, or worse than water at dissolving salt? Alcohol does not dissolve salt as well as water does. How do you know? There was more salt left behind in the cup with the alcohol. Think about the polarity of water and alcohol to explain why water dissolves more salt than alcohol. Have students look at the models of water and alcohol molecules on their activity sheet.

Extend Have students compare the solubility of two different ionic substances in water. Ask students: How could you compare the solubility of calcium chloride and calcium carbonate? Students should suggest measuring equal amounts of each substance and adding equal amounts of water at the same temperature. Question to Investigate Do all ionic substances dissolve in water? Measure 2 g each of sodium carbonate and calcium carbonate and put them in their labeled cups. Measure 15 mL of water into each of two empty cups.

At the same time, pour the water into the sodium carbonate and calcium carbonate cups. Each minor component of a solution and there may be more than one is called the solute. In most of the solutions we will describe in this textbook, there will be no ambiguity about whether a component is the solvent or the solute. For example, in a solution of salt in water, the solute is salt, and solvent is water. Solutions come in all phases, and the solvent and the solute do not have to be in the same phase to form a solution such as salt and water.

An alloy is a solid solution consisting of a metal like iron with some other metals or nonmetals dissolved in it. Steel, an alloy of iron and carbon and small amounts of other metals, is an example of a solid solution. What causes a solution to form? The simple answer is that the solvent and the solute must have similar intermolecular interactions.

When this is the case, the individual particles of solvent and solute can easily mix so intimately that each particle of solute is surrounded by particles of solute, forming a solution. However, if two substances have very different intermolecular interactions, large amounts of energy are required to force their individual particles to mix intimately, so a solution does not form. This process leads to a simple rule of thumb: like dissolves like.

Solvents that are very polar will dissolve solutes that are very polar or even ionic. Solvents that are nonpolar will dissolve nonpolar solutes. Thus water, being polar, is a good solvent for ionic compounds and polar solutes like ethanol C 2 H 5 OH.

The two fluids cannot mix and the dye cannot dissolve in fluorocarbon. A goldfish and a crab have been introduced into the water. The goldfish cannot penetrate the dense fluorocarbon.