a) The equations for the dissolution of Calcium Chlorideand sodium bicarbonate i
ID: 675628 • Letter: A
Question
a) The equations for the dissolution of Calcium Chlorideand sodium bicarbonate in water.
(b) Look up the Heats of solutions for calcium chlorideand sodium bicarbonate (indicate exothermic or endothermicreactions)
(c) Look up the solubility’s of these two salts andany other salts that may form in Ziploc bag.
(d) Write out the equations for the neutralizing of a strongacid with a strong base.
(e) Write out the K(a) and K(b) for the bicarbonate ionwith chemical equation.
(f) The Ph range for the indicator bromothymol blue.
Explanation / Answer
(a) I think this is just asking you to write the equations for thedissociation of calcium chloride (CaCl2) and sodiumbicarbonate (NaHCO3) into their constituent ions. Bothof these compounds are ionic. Also, Sodium bicarbonate is alsoknown as sodium hydrogen carbonate. CaCl2(s) --> Ca2+(aq) +2Cl-(aq) NaHCO3(s) -->Na+(aq) + HCO3-(aq) There might also be: CaCl2 + 2NaHCO3 -->CaCO3 + 2NaCl + H2O + CO2 For sodium bicarbonate, you could also write the equilibriumreactions: HCO3- + H2O H2CO3 + OH- H2CO3 CO2(g) +H2O Not sure if these equations are relevant to the course you'redoing... (b) Calcium chloride: -81.3 kJ/mol(http://www.philasim.org/newmanual/exp30.pdf) Sodium Bicarbonate: 33.6 kJ/mol(http://answers.yahoo.com/question/index?qid=20080224175429AAr5Yg1) Sorry I couldn't find bettersources... =S A positive heat of solutionindicates heat gain by the compound = endothermic. A negative heatof solution indicates heat loss by the compound = exothermic.Therefore Calcium chloride dissolution is exothermic, while sodiumbicarbonate dissolution is endothermic.(http://www.wwnorton.com/college/chemistry/gilbert/concepts/chapter13/ch13_1.htm) (c) Calcium chloride: 81.3 g per 100 g H2O Sodium hydrogen carbonate: 10.3 gper 100 g H2O Source: CRC Handbook of Chemistryand Physics, Section 4, Physical Constants of Inorganic Compounds(http://www.hbcponline.com/) Looking at the ions present (Na+, Cl-,HCO3-, Ca2+, OH-,CO32-), you might also expect to find: NaCl; solubility = 36.0 g per 100 g water NaOH (not a salt) Ca(HCO3)2; solubility =16.6 g per 100 g water (wikipedia) Ca(OH)2 (not a salt??) CaCO3; solubility = 0.00066 g / 100 gwater (i.e. not very soluble!) (d) Acid + Base --> Salt + Water HA + BOH --> AB +H2O, or simply: e.g. HCl + NaOH --> NaCl + H2O Note that the reaction goes to completion, since we are dealingwith strong acids and bases. Hence we use the 'one-sided' arrow,and not the equilibrium arrow. (e) See (a) for chemical equation. You can find the constants on the wikipediapage: http://en.wikipedia.org/wiki/Carbonic_acid (f) Bromothymol blue turns from yellow to blue at pH 6 - pH 7.6.(from CRC handbook, link stated earlier on) Hope your first prac goes well! They're really not that scary onceyou do a couple =)Related Questions
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