Mass solute

In the Bom-Oppenheimer picture the nuclei move on a potential energy surface (PES) which is a solution to the electronic Schrodinger equation. The PES is independent of the nuclear masses (i.e. it is the same for isotopic molecules), this is not the case when working in the adiabatic approximation since the diagonal correction (and mass polarization) depends on the nuclear masses. Solution of (3.16) for the nuclear wave function leads to energy levels for molecular vibrations (Section 13.1) and rotations, which in turn are the fundamentals for many forms of spectroscopy, such as IR, Raman, microwave etc. 

Notes (a) Cobalt(II) 2-ethylhexanoate, 65% mass solution in mineral spirits (b) 2-butanone peroxide, ca. 32% mass solution in dimethyl o-phthalate. 

Colligative properties can be sources of insight into not only the properties of solutions, but also the properties of the solute. For example, acetic acid, CH.COOH, behaves differently in two different solvents, (a) The freezing point of a 5.00% by mass aqueous acetic acid solution is — l.72°C. What is the molar mass of the solute Explain any discrepancy between the experimental and the expected molar mass, (b) The freezing-point depression associated with a 5.00% by mass solution of acetic acid in benzene is 2.32°C. Whar is the experimental molar mass of the solute in benzene What can you conclude about the nature of acetic acid in benzene ... 

To understand this in more detail, we can consider the liquid to be based on a lattice arrangement. For low molar mass solutes, each point in the lattice can be considered to be occupied by either a solvent or solute molecule. The possible arrangements of solute and solvent molecules in an extensive lattice will be very large, as shown in Figure 5.1a. According to the Boltzmann equation. 

If we now put a polymer into this lattice, we can no longer place one molecule of solute at each lattice site. Instead, we can put only one segment of the polymer molecule at any one lattice site, as shown in Figure 5.1b. When we do this we see that there are many fewer possible arrangements for the system. The value of W is thus much lower than for the low molar mass solute, hence so is 5. 

Figure 5.1 Lattice arrangements for (a) low molar mass solute in solution and (b) polymer in solution...

The heat of mixing for polymer solutions, by analogy with solutions of low molar mass solutes, is given by ... 

Mass/volume % = (mass solute/volume of solution) x 100%... 

A 1.00% NaCl(aq) by mass solution has a freezing point of —0.593°C. (a) Estimate the van t Hoff i factor from the data, (b) Determine the total molality of all solute species, (c) Calculate the percentage dissociation of NaCl in this solution. (Hint The molality calculated from the freezing-point depression is the sum of the molalities of the undissociated ion pairs, the Na+ ions, and the Cl ions.)... 

The mass percent of a sol tiory is the mass of the solute divided by the total mass (solute + solvent) multiplied by 100. 

Ethylene glycol, C2HgC>2, is the principal constituent of automobile antifreeze. If the density of a 40.0 mass % solution of ethylene glycol in water is 1.0514 g/mL at 20°C, what is the molarity ... 

What is the molality of the 16.0 mass % solution of sulfuric acid in Problem 11.60 ... 

Assuming that seawater is a 3.5 mass % solution of NaCl and that its density is 1.00 g/mL, calculate both its boiling point and its freezing point in °C. 

Rubbing alcohol is a 90 mass % solution of isopropyl alcohol, C3H8O, in water. 

A 7.0 mass % solution of H3PO4 in water has a density of 1.0353 g/mL. Calculate the pH and the concentrations of all species present (H3PO4, H2PO4-, HPO42-, P043-,H30+, and OH-) in the solution. Values of equilibrium constants are listed in Appendix C. 

Figure 4.11. Diagram showing the use of Lockspray to introduce a lock mass solution into an ESI source of a Q-TOF mass spectrometer.

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