Concept explainers
Interpretation:
The process of dissolving
Concept Introduction:
Dissolving ionic solids in liquids: On dissolving ionic solids in water, water molecules surround cations and anions are called hydration.
Hydration enthalpy is defined asthe enthalpy change when new attractions form between ions and water-molecule dipoles. Energy always that require to separate the ions from crystal lattice, and energy always released when ions become hydrated because molecular dipoles attract the molecules to the ions.
The relation between the enthalpy of solution as follows,
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OWLv2 for Moore/Stanitski's Chemistry: The Molecular Science, 5th Edition, [Instant Access], 1 term (6 months)
- a. Use the following data to calculate the enthalpy of hydration for calcium chloride and calcium iodide. Lattice Energy Hsoln CaCl2(s) 2247kj/mol 46kj/mol Cal2(s) 2059kj/mol 104kj/mol b. Based on your answers to part a, which ion, Cl or I, is more strongly attracted to water?arrow_forwardWhat is the freezing point and normal boiling point of a solution made by adding 39 mL of acetone, C3H6O, to 225 mL of water? The densities of acetone and water are 0.790 g/cm3 and 1.00 g/cm3, respectively.arrow_forwardWater at 25 C has a density of 0.997 g/cm3. Calculate the molality and molarity of pure water at this temperature.arrow_forward
- What would be the freezing point of a solution formed by adding 1.0 mole of glucose (a molecular compound) to the following amounts of water? a. 250 g (0.25 kg) b. 500 g (0.500 kg) c. 1000 g (1.000 kg) d. 2000 g (2.000 kg)arrow_forwardA forensic chemist is given a white solid that is suspected of being pure cocaine (C17H21NO4, molar mass = 303.35 g/mol). She dissolves 1.22 0.01 g of the solid in 15.60 0.01 g benzene. The freezing point is lowered by 1.32 0.04C. a. What is the molar mass of the substance? Assuming that the percent uncertainty in the calculated molar mass is the same as the percent uncertainty in the temperature change, calculate the uncertainty in the molar mass. b. Could the chemist unequivocally state that the substance is cocaine? For example, is the uncertainty small enough to distinguish cocaine from codeine (C18H21NO3, molar mass = 299.36 g/mol)? c. Assuming that the absolute uncertainties in the measurements of temperature and mass remain unchanged, how could the chemist improve the precision of her results?arrow_forwardFreezing point depression is one means of determining the molar mass of a compound. The freezing point depression constant of benzene is 5.12 C/m. a. When a 0.503 g sample of the white crystalline dimer is dissolved in 10.0 g benzene, the freezing point of benzene is decreased by 0542 C. Verify that the molar mass of the dimer is 475 g/mol when determined by freezing point depression. Assume no dissociation of the dimer occurs. b. The correct molar mass of the dimer is 487 g/mol. Explain why the dissociation equilibrium causes the freezing point depression calculation to yield a lower molar mass for the dimer.arrow_forward
- Sodium chloride (NaCl) is commonly used to melt ice on roads during the winter. Calcium chloride (CaCl2) is sometimes used for this purpose too. Let us compare the effectiveness of equal masses of these two compounds in lowering the freezing point of water, by calculating the freezing point depression of solutions containing 200. g of each salt in 1.00 kg of water. (An advantage of CaCl2 is that it acts more quickly because it is hygroscopic, that is. it absorbs moisture from the air to give a solution and begin the process. A disadvantage is that this compound is more costly.)arrow_forward6-111 As noted in Section 6-8C, the amount of external pressure that must be applied to a more concentrated solution to stop the passage of solvent molecules across a semipermeable membrane is known as the osmotic pressure The osmotic pressure obeys a law similar in form to the ideal gas law (discussed in Section 5-4), where Substituting for pressure and solving for osmotic pressures gives the following equation: RT MRT, where M is the concentration or molarity of the solution. (a) Determine the osmotic pressure at 25°C of a 0.0020 M sucrose (C12H22O11) solution. (b) Seawater contains 3.4 g of salts for every liter of solution. Assuming the solute consists entirely of NaCl (and complete dissociation of the NaCI salt), calculate the osmotic pressure of seawater at 25°C. (c) The average osmotic pressure of blood is 7.7 atm at 25°C. What concentration of glucose (C6H12O6) will be isotonic with blood? (d) Lysozyme is an enzyme that breaks bacterial cell walls. A solution containing 0.150 g of this enzyme in 210. mL of solution has an osmotic pressure of 0.953 torr at 25°C. What is the molar mass of lysozyme? (e) The osmotic pressure of an aqueous solution of a certain protein was measured in order to determine the protein's molar mass. The solution contained 3.50 mg of protein dissolved in sufficient water to form 5.00 mL of solution. The osmotic pressure of the solution at 25°C was found to be 1.54 torr. Calculate the molar mass of the protein.arrow_forwardThe dispersed phase of a certain colloidal dispersion consists of spheres of diameter 1.0 102 nm. (a) What are the volume (V=43r2) and surface area (A = r2) of each sphere? (b) How many spheres are required to give a total volume of 1.0 cm3? What is the total surface area of these spheres in square meters?arrow_forward
- Consider two solutions, A and B, separated by an osmotic semipermeable membrane that allows only water to pass through, as shown in the diagram in Problem 8-113. Based on each of the following identities for solutions A and B, indicate whether the liquid level in compartment A, with time, will increase, decrease, or not change. a. A = 1.0 M glucose solution and B = 2.0 M glucose solution b. A = 5.0%(m/v) NaCl solution and B = 4.0%(m/v) NaCl solution c. A = 2.0 M Na2SO4 solution and B = 3.0 M KNO3 solution d. A = 2.0 M glucose solution and B = 1.0 M NaCl solutionarrow_forwardConsider three test tubes. Tube A has pure water. Tube B has an aqueous 1.0 m solution of ethanol, C2H5OH. Tube C has an aqueous 1.0 m solution of NaCl. Which of the following statements are true? (Assume that for these solutions 1.0m=1.0M.) (a) The vapor pressure of the solvent over tube A is greater than the solvent pressure over tube B. (b) The freezing point of the solution in tube B is higher than the freezing point of the solution in tube A. (c) The freezing point of the solution in tube B is higher than the freezing point of the solution in tube C. (d) The boiling point of the solution in tube B is higher than the boiling point of the solution in tube C. (e) The osmotic pressure of the solution in tube B is greater than the osmotic pressure of the solution in tube C.arrow_forwardRefer to Figure 13.10 ( Sec. 13-4b) to determine whether these situations would result in an unsaturated, saturated, or supersaturated solution. 120. g RbCl is added to 100. g H2O at 50 °C. 30. g KCl is dissolved in 100. g H2O at 70 °C. 20. g NaCl is dissolved in 50. g H2O at 60 °C. Figure 13.10 Solubility of ionic compounds versus temperature.arrow_forward
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