K Preparing Solutions

The question that students ask most frequently when preparing solutions is, Is this dissolved That question must be answered by visual inspection that you can perform easier than your instructor. The key is to 

A gas can be dissolved in a liquid solvent in which it is soluble by bubbling the gas through the liquid. Normally stirring is not necessary because the bubbling provides sufficient mixing. Thus, red-brown nitrogen dioxide, NO2, gas can be bubbled into water and does not escape from the water because it dissolves. Conversely, colorless hydrogen, H2, gas bubbles into and out of water because H2 is insoluble in water. 

One liquid can be dissolved in another liquid with which it is miscible if the two liquids are poured together and stirred or shaken. Thus, ethanol, CH3CH2OH, and water mix in all proportions to form a solution whereas cyclohexane, C6Hi2f forms a layer above water after the two are stirred in a test tube. It is important to stir aqueous solutions when performing chemical reactions because aqueous solutions do not mix readily, especially if they have quite different densities and are in narrow test tubes. 

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