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Date : Page : Solutions A. solution (s @ homogeneous mixture of two or more chemically non-reacting suestances whose 7 9 j composition can be varied within certain limits. Solvent :: stete component in larger amount. Solute : the component in smaller amount. Binary solution +: one solute + one solvent. Types of Solutions Based on the physical state of solute & Solvent, q types of solutions are possible Gas in gas : air (02 + M2 + ..) Gas in lig + 02 in water, soda Gas in sol : H2 in Pd, Pr Lig in gas * molsture in air Lig in hig ¢ alcohol in’ water Lig in sol s amalgam Hg in Ya) Sol in Gas * camphor in air Sol in Ng : salt in water ©©OOODOOHO Sol in sol + alloys (erass, bronze) Most common type : solid / liguid in Iiguid. 1 ‘Scamed with GamScanner Date : Page : 2 Concentration of Solutions Concentration = amount of solute in a given quantity of solution / solvent. Several methods: CG) Mass Percentages (w/w) / | wlw % = (mass of solute / mass of soln)|x /0O0 ees <-e.g. 10 % glucose soin » 10 g glucose in <-7O 9 water ~ (total JOO g soln). (2) Volume Percentage (Ju) v/e % = ol. of solute / vol. of soln) x| /OO — — ae J 3% v/v ag. ethylene glycol + antifreeze in car radiators ( freezes at -/7.6 C ). (3) Mass wy Volume (w/V) whl % = (mass of solute / vol. soln) x JOO * <-used in medicine & pharmacy. x Mote : w/V depends on temperature (V changes). ‘Seamed with GamScanner Date : Page : a Molarity & Molality — () Molarity (Ww + Moles of solute dissolved per litre of solution. Man oy V Gr iL? | <-unit 2 mol/L Solute <-= M4 Also MM z (uw, x 4000) / (M, x WV mb) Drawback : depends on T (volume, expands / contracts with T?. Hence MOT temp-independent. C7) Melality Cm) “Moles of solute per Kg of Solvent. (xg) | O7 Solubility increases with T C Kaz ?. LF exothermic (delta H < 0) Solubility decreases with T € Ce2(S09)2 ?. Pressure : negligible effect on solid Solubility. ‘Scanned with GamScanner Date : Page : Solubility of Gas in Liguid Strongly affected by Temperature & Pressure. Henry's Law At constant T, solubility of a gas in a liguid is directhy Proportional to its partial pressure. 2 ie Ka <-KH = Henry's law <-canstant, P = partial pressure of gas above soln x = mole fraction of gas in soln Plot oP SUS aX, Higher Kit P BP dewer lope = Ki a SEES Solubility S aS of gas. ee Gas) ‘Scamed with GamScanner Date : Page : 10 Solved Examplh 3 Qa 2 gas Is bubbled through water at 293 —K EF p (2) = 0.997 bar, calculate moles of M2 dissolved in / L water. KH(W2) = 76.9% kbar. Solution + By Henry's law : p = Ky x Xap 2p / Ky = O9F7 ((I6TIO) = 129 3 IO JL water = J000 g =? 1000//F = FF.EE5 mol X42 Pn / H20 (since Race 2 Pitre? LAY Irie el Xian, a2 Se) II (OU Oe So Se ne) = LIC x JO = 3-4 mol, Very little M2 dissolves at / atm im pure water - because KH(v2) is high. ‘Seamed with GamScanner Date : Page : uM Vapour Pressure - Faoult's Law Vapour Pressure (VP) Pressure exerted by vapour in eguilibrivm with its liguid Ate: given temperature. Raoult's Law Clig-lig solution) For a solution of volatile liguids, the partial VP of each component Is directly Proportional to its mole fraction in the solution. = a = * -p® = VP of PASS Bae | | Bree eas Bs e <-pure component By Dalton's law of partial pressures = eee * Pterai_=_ Pat Pe = Py *, t Pe Xs Since sx, = 72 xs we * * Pau = Pa dee ee, =7 p_total varies linearly with xB. ‘Scamed with GamScanner Date : Page : 43 ideal & Mon-ideal Solutions Ideal Solution - Obeys Raoult's law for ALL compositions and all temperatures. Conditions [Oe A cal pax x At and p28 = pis x _B @ delta_mix H =z O (no heat change) @) delta_.mix V = O (no vol. change) @) FIA-A) = FB-B) = F(A-B) Examples : n-hexane + n-heptane benzene + toluene CcCcly + SiICIP (chlorides? Men- ideal Solution Does AOT obey Kaoult's law. F(A-8) %=z FCA-A), FB-8) =7 ~~ shows deviation. | Two types D+ ve du : FA-B) < F(A-A), FB-B) VP higher than predicted wy Faoult's law. G2 te A 2 FAA), 8-8) VP lower than predicted by Faoult's law. ‘Scamed with GarSeanner Date : Page : Deviation P lots (a)? Positive Deviation Examples a ethanol + acetone cclry + Coto CS2 + acetone Er0oH + H20 H-bonding in pure ethanol wreaks =7 more vapours. (e) Megative Deviation Examples + CHCIZ + acetone Hei + 120 Ha03z + H20 Peew H-bond btwn cHeiz & cH3-c0-cH3 =7 VP lowered. xA=/ xBo/ ‘Scanned with CamScanner Date: _. Page : fe Solid Solute in _Liguid Solvent Mon-volatile solute does MOT contribute to VP. So p_solution = p/ = pre x/ (Raoult? where / = solvent ; non-vol. solute (2) has pe. = 0; / Relative Lowering of VP VP of solvent in solution < VP of pure solvent. Eee ee <-depends only on &, Pp? / Py ay) <-x2 (colligative) Derivation | iO 2h ret len BES For dilute solution Gn2. << n/) r, fp bw JM) # Cw Jan )* x, a 27 (ph pip oe Allows molar mass determination of solute. AG ‘Scamed with GamScanner Date : Page : ‘7 Colligative Properties Properties of dilute solutions that depend OALY on the number of Solute particles, and MOT on their nature. Four colligative properties @) Relative lowering of VP @) Elevation of boiling point @) Depression of Freezing point () Osmotic pressure (2) Elevation of BP BP of solvent rises when a non-volatile solute is added. delta T_b = To - Te™. ah Silene” delta Tee = Kn <-Ko = molal BP \ a e <-elev. const. Ke units is K Kg / mol (er ~ Cc Kg / mol). b Ko = OM 7 ff YOoo delta H) Ko (water) = O.€2 K g/mol j. Ke (cele) = ‘Scamed with GamScanner 233 Date: __ Page : 4 Osmosis & Osmotic Pressure Osmosis : spontaneovs flow of solvent molecules from a pure Solvent lor dilute soln) to a concentrated soln through a Semipermeable membrane (SPA). - Osmotic pressure, (pi) = extra pressure that must be applied on the solution side to JUST stop osmosis. : * Pili else (rn fv) ha <-Van't Hoff <- eguation C = molar conc. (mol/L) ; R = 0.0%2/ L atm/mol K T in Kelvin ¢ pi in atm. sPat solution solvent Onigh cond ig Cow cond + solvent flow -7 A gives a measure of osmotic pressure. ‘Scamed with GamScanner 2 Date : Page: 20 Osmosis - Terminology & Uses Lsotonic, Hyper-, Hypotonic @ Lsotonic 2. two soln of equal pl eg. -0.9% waci & blood plasma at 3/0 K. ® Hypertonic £ Salm with higher pl. Water exits cell -7 “shrinks (crenation). @) Hypotonic 2 Soln with lower pi. Water enters cell -7 bursts Chaemoly sis). Reverse Osmosis If P_applied 7 pi on the solution side, solvent flows from solution -F7 pure side. Used in desotrrzahorr desalination of sea water. Why pi_is preferred (not delta To / TP Gi) Magnitude of pi is large =7 measurable even for very dilute Solutions: Gi? Measured at room T tunlike BP / FP). Git) Suitaple for proteins, polymers which decompose at high Te ‘Scamed with GarScanner 
