# Water Section C Flashcard

 Define a saturated solution.   Use the terms solvent and solute.
 A solution is saturated when the solvent (usually water) has dissolved the maximum amount of solute.
 If you want to dissolve a greater amount of salt in a solution, what should you do with the temperature?
 Since salt is an ionic compound, then raising the temperature will allow you to dissolve a greater amount of salt.
 What is the solubility of KNO3 at 35 °C?
 According to the solubility curve, the solubility is   55 g of KNO3 in 100 g H2O   at 35 °C.
 With increasing temperature, the solubility of a gas (increases/decreases).
 decreases
 You have 80 grams of 20 ºC water, and 50 grams of KNO3.   Explain how you would make a saturated solution of KNO3 with these materials.
 Since the solubility of KNO3 at this temperature is about 30 grams in 100 grams of water, which is equivalent to 24 grams of KNO3 in 80 grams of water, you would measure out 24 grams of KNO3 and dissolve it in the 80 grams of water.
 A saturated solution of NH4Cl made with 100 grams of water, is initially at 90 ºC.   You then let the solution cool to 5 ºC.   How many grams of NH4Cl will precipitate out of solution at 5 ºC?
 70 g – 30 g = 40 g   40 grams will precipitate out.
 You think you are in possession of a saturated solution of NaCl.  But you want to be sure.   Explain how you could use a single crystal of NaCl to find out.
 Add the single crystal to the solution.  If the crystal does not dissolve, then the solution was saturated.   If the crystal does dissolve, then the solution was unsaturated.
 Calculate the pph concentration of a saturated solution of potassium iodide at 20 ºC.
 According to the solubility curve, the solubility at 20 ºC is about 145 g KI/100 g H2O.   So, the pph concentration is calculated by dividing the mass of the solute by the total mass of the solution.               145 =   x          solve for x, get 59 pph             245     100
 A sample of river water is found to have a lead(IV) concentration of 18 ppm.   How many grams of lead(IV) ion are in a 450 kg sample of this river water?
 18 ppm means 18 kg of lead(IV) ion dissolved in 1,000,000 kg of river water sample.  So set up the following ratio:         18      =     x            solve for x, get 0.0081 kg.  1,000,000      450 kg   But since they ask for the grams, 0.0081 kg is 8.1 grams.
 If 14 grams of sodium nitrate is dissolved in 75 grams of water, calculate the pph concentration.
 14  =     x          solve for x, get 15.7 pph.             89       100
 A solution of 80 grams of NH3 dissolved in 200 grams of water at 15 ºC is (saturated/unsaturated/supersaturated).
 Unsaturated.   At 15 ºC, the solubility of NH3 is 60 grams per 100 grams of water, which is equivalent to 120 grams per 200 grams of water.   Since only 80 grams of NH3 are dissolved, then the solution is unsaturated.
 A chemist dissolves 30 grams of potassium chloride in 100 grams of water at 50 ºC.  The solution is unsaturated.   How many more grams of solute need to be added to make the solution saturated?
 10 more grams.
 A Na+ solution has a concentration of 8 pph.  Describe how mnay grams of solute and solvent are in a 100 gram sample of this solution.
 8 pph means that 8 grams of sodium ion are dissolved in 92 grams of water.
 A solution is classified as a base if the concentration of which ion (H+ or OH–) is greater?
 OH– concentration is greater.
 Name this ion:   OH–
 hydroxide ion.
 A solution having a pH=6 is classified as a(n) (acid / base).
 Acid.
 How does the concentration of H+ in solutions with pH values of 4 and 7 compare?
 Since the pH difference is 3, the concentration difference is   10 x 10 x 10 = 1000 times difference in concentration.
 Give two examples of heavy metals.
 If an unknown clear liquid is miscible with water, the unknown liquid is classified as (polar/nonpolar).
 Polar.
 Salt dissolves in water, but not in acetone.    Therefore acetone is (polar/nonpolar).
 Nonpolar.
 Explain why water is a polar molecule.
 Water is a polar molecule because the two bonds in water have unequally-shared electrons.   As a result, the molecule has partial charges on it.
 Draw two water molecules, showing the partial charges on each molecule.   Then show a hydrogen bond between the two molecules.
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 Which solute – NaNO3, NH4Cl or or NaCl – has a greater temperature dependence on its solubility?
 NaNO3.  This solute has the largest slope of the three solubility lines.
 Clove oil is a dark brown, denser-than-water nonpolar liquid.   If you mix water, CuSO4 and clove oil together, what would the resulting mixture look like?  Discuss colors.
 The CuSO4 would dissolve in the water, and the clove oil and water/CuCO4 solution would make separate layers, with the clove oil on the bottom.   So the top layer would be a clear or slightly blue solution, and the bottom layer would be dark brown.