(a)(i) Explain what is meant by saturated solution
(ii) Describe in outline, a suitable procedure for preparing a saturated solution of sodium trioxonitrate(V) at 30°C.
(ii) State two techniques that can be used to recover crystals of sodium trioxonitrate(V) from its saturated solution.
(b) 1.0dm\(^3\) of an aqueous solution at 90°C contains 404g of potassium trioxonitrate(V) and 245g of potassium trioxochlorate (V).
(i) Determine which of the two salts will separate out when the solution is cooled to 60°C. N = 14. O = 16, CI = 35.5, K = 39; Solubility of KNO\(_3\) in water at 60\(^o\)C = 5.14 mol.dm\(^{-3}\), Solubility of KCIO\(_3\) in water at 60°C = 1.61 mol.dm\(^{-3}\)
(ii) Calculate the mass of salt that will separate out at 60°C
(c)(i) List two salts which cause hardness of water.
(ii) Explain why temporary hardness of water result in the furring of kettle.
a)(i) Saturated solution: A saturated solution is a solution that has dissolved the maximum amount of solute at a given temperature and pressure, where any additional solute will remain undissolved at the bottom of the container.
a)(ii) Preparation of saturated solution: To prepare a saturated solution of sodium trioxonitrate(V) at 30°C, a known mass of the solute is added to a fixed volume of solvent (water) at 30°C, and stirred continuously until no more solute dissolves, and some amount remains undissolved.
a)(iii) Recovery techniques: Two techniques that can be used to recover crystals of sodium trioxonitrate(V) from its saturated solution are cooling the solution, which will cause the excess solute to crystallize out, and evaporation of the solvent, which will leave the solute behind as crystals.
b)(i) Separation of salts: To determine which of the two salts will separate out when the solution is cooled to 60°C, we need to compare the solubility of each salt at 60°C with the concentration of each salt in the solution at 90°C. The solubility of KNO3 in water at 60°C is higher than the solubility of KCIO3 in water at 60°C, so KNO3 will remain in solution while KCIO3 will separate out.
b)(ii) Calculation of mass: To calculate the mass of salt that will separate out at 60°C, we need to use the solubility data and the concentration of KCIO3 in the solution. The amount of KCIO3 in the solution at 90°C is 245g, which is equal to 245/122 = 2.01 mol. At 60°C, the solubility of KCIO3 is 1.61 mol.dm-3, so the maximum amount of KCIO3 that can remain in solution is 1.61 mol. Therefore, the amount of KCIO3 that will separate out is 2.01 - 1.61 = 0.40 mol. The molar mass of KCIO3 is (39+35.5+3x16) = 122g/mol, so the mass of KCIO3 that will separate out is 0.40 x 122 = 48.8g.
c)(i) Salts causing hardness of water: Two salts that cause hardness of water are calcium carbonate (CaCO3) and magnesium sulfate (MgSO4).
c)(ii) Temporary hardness of water: Temporary hardness of water is caused by the presence of dissolved calcium and magnesium bicarbonates, which can decompose upon heating, leading to the formation of insoluble calcium and magnesium carbonates. These carbonates deposit as a layer of scale (furring) on the inside of kettles and other hot water equipment.
a)(i) Saturated solution: A saturated solution is a solution that has dissolved the maximum amount of solute at a given temperature and pressure, where any additional solute will remain undissolved at the bottom of the container.
a)(ii) Preparation of saturated solution: To prepare a saturated solution of sodium trioxonitrate(V) at 30°C, a known mass of the solute is added to a fixed volume of solvent (water) at 30°C, and stirred continuously until no more solute dissolves, and some amount remains undissolved.
a)(iii) Recovery techniques: Two techniques that can be used to recover crystals of sodium trioxonitrate(V) from its saturated solution are cooling the solution, which will cause the excess solute to crystallize out, and evaporation of the solvent, which will leave the solute behind as crystals.
b)(i) Separation of salts: To determine which of the two salts will separate out when the solution is cooled to 60°C, we need to compare the solubility of each salt at 60°C with the concentration of each salt in the solution at 90°C. The solubility of KNO3 in water at 60°C is higher than the solubility of KCIO3 in water at 60°C, so KNO3 will remain in solution while KCIO3 will separate out.
b)(ii) Calculation of mass: To calculate the mass of salt that will separate out at 60°C, we need to use the solubility data and the concentration of KCIO3 in the solution. The amount of KCIO3 in the solution at 90°C is 245g, which is equal to 245/122 = 2.01 mol. At 60°C, the solubility of KCIO3 is 1.61 mol.dm-3, so the maximum amount of KCIO3 that can remain in solution is 1.61 mol. Therefore, the amount of KCIO3 that will separate out is 2.01 - 1.61 = 0.40 mol. The molar mass of KCIO3 is (39+35.5+3x16) = 122g/mol, so the mass of KCIO3 that will separate out is 0.40 x 122 = 48.8g.
c)(i) Salts causing hardness of water: Two salts that cause hardness of water are calcium carbonate (CaCO3) and magnesium sulfate (MgSO4).
c)(ii) Temporary hardness of water: Temporary hardness of water is caused by the presence of dissolved calcium and magnesium bicarbonates, which can decompose upon heating, leading to the formation of insoluble calcium and magnesium carbonates. These carbonates deposit as a layer of scale (furring) on the inside of kettles and other hot water equipment.
