Stpm Sem 2 Chemistry Experiment 2013

Topics: Hydrochloric acid, Sodium chloride, Solubility Pages: 6 (1784 words) Published: August 21, 2013
Experiment 6 :Observation | KA2| KA3|
Weight of test-tube + solid / g | | |
Weight of empty test-tube / g | X1
| X2
|
Weight of solid / g | | |
Initial temperature of acid / °C | | |
Final temperature of mixture / °C | θ1
| θ2
|
Temperature change / °C | | |
Discussion :[In the experiment sheet, the is an error where questions in (c)(i) should be "the heat change involved the reactions involving KA2 and KA3] (c). i : q1 = mcθ1 ; q = (30.00)(4.18)( θ1) = q1 q2 = mcθ2 ; q = (30.00)(4.18)( θ2) = q2ii. mol of KA2 = mass / RMM ; mol of KA2 = x1 / 84 = a1 mol of KA3 = mass / RMM ; mol of KA3 = x2 / 106 = a2iii. HKA2 = q1 / a1 = - P kJ / molHKA3 = q2 / a2 = +Q kJ / mol(d)KA2 + KA1 : Na2CO3(s) + 2 HCl (aq) → 2NaCl(aq) + H2O(l) + CO2 (g)KA3 + KA1 : NaHCO3 (s) + HCl (aq) → NaCl (aq) + H2O (l) + CO2 (g)(e) Energy Na2CO3 (s) + 2 HCl (aq) + H2O (l) + CO2 (g)HKA2

/ kJ H
2 x HKA3
2 NaCl (aq) + 2 H2O (l) + 2 CO2 (g)2 NaHCO3 (s) + 2 HCl (aq)(f) Na2CO3(s) + 2 HCl (aq) → 2NaCl(aq) + H2O(l) + CO2 (g) [1]HKA2 = - P kJ NaHCO3 (s) + HCl (aq) → NaCl (aq) + H2O (l) + CO2 (g)[2]HKA3 = + Q kJ Reverse equation [1]2NaCl(aq) + H2O(l) + CO2 (g) → Na2CO3(s) + 2 HCl (aq) HKA2 = + P kJ / mol2 NaHCO3 → Na2CO3(s) + H2O +CO2 Hrxn = +P + 2(Q) kJ| Experiment 7 :Procedures -1. Set-up the apparatus as shown in the diagram below | 2. Using sand paper, both copper plates were brushed, and then dipped into propanone, followed by drying both plates using hair drier.| 3. Both plates were then weigh separately and were recorded as initial mass of anode and cathode in the table below.4. Both weighed plate were clipped using crocodile clips and the batteries were placed in the battery socket. After that, both plates were immersed in copper (II) solution and the stop watch was started to allow the apparatus to run for 30 minutes.5. the reading of ammeter was recorded. Then, both plates were taken out from the solution, and were dipped into propanone, before blow to dry for both plates using hair drier.6. The dried plates were then weighed and were recorded as final mass accordingly. The mass lost (at anode) and gained (at cathode) were calculated.Observation : | Copper (anode)| Copper (cathode)| Initial mass / g| Xinitial| Yinitial|

Final mass / g| Xfinal| Yfinal|
Difference / g| X| Y|
Time taken : 30 minutesCurrent used : p ADiscussion :The current used : Q = It ; Q = (p)(30 x 60) = a CMol of e- used = Q / F @ a / 96500 ; mol of e- = d molAt anode, since Cu → Cu2+ + 2 e- ; 1 mol of Cu = 2 mol of e-Mass of copper dissolved = d mol / 2 x 63.5 g = f g % of purity of Cu = mass gained at cathode / mass of Cu dissolve= Y / f x 100%[Note that your mass of Cu gained must be less than Cu dissolved]| | |

Experiment 8 :
Suggested salts for KA1 is MgS2O3 or MgSO3 or CuSO3 or Pb(CH3COO)2 or Ca(CH3COO)2 | Observation| Deduction|
(b) Add dilute hydrochloric acid to a small amount of solid KA 1, then warm gently. | If S2O32- : Yellow precipitate; brimstone [pungent] smell gas/ gas decolourise KMnO4/H+| S2O32- may present| | If SO32- : brimstone smell gas/ gas decolourise KMnO4/H+| SO32- may present| | If CH3COO- : Gas smell of vinegar is released when heated| CH3COO- " present| (c) Dissolve solid KA 1 in distilled water and filter. Use separate portions of the filtrate for tests (i) to (vi). (i) Add aqueous NaOH, then in excess. | i. White precipitate insoluble in excess NaOH| Mg2+ , Ca2+ may present| | ii. White precipitate soluble in excess NaOH| Pb2+,Zn2+,Al3+ may present| | Blue precipitate insoluble in excess NaOH| Cu2+ may present| (ii) Add aqueous NH3, then in excess followed by aqueous NH4Cl| White precipitate insoluble in excess NH3 (if (i) is fulfilled)| Mg2+ confirm present| | White precipitate insoluble in excess NH3 (if (ii) is fulfilled)| Pb2+ , Al3+ present| | No precipitate formed...
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Chemistry Experiment Essay
  • Essay on Experiment 2 Formal Report
  • Essay on chemistry report
  • Chemistry Experiment Essay
  • Chemistry Essay
  • Essay about Chemistry Experiment
  • chemistry Essay
  • Essay on Chemistry Experiment

Become a StudyMode Member

Sign Up - It's Free