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Hess's Law Lab Report

  • Date Submitted: 06/06/2011 02:22 AM
  • Flesch-Kincaid Score: 78.2 
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Data Collection:

Qualitative Observation:
The first chemical added to HCl was Na2CO3(s) and bubbles were formed as soon as the Sodium Anhydrous Carbonate powder was added. The color of the reaction looked like a light purple violent color. There was no specific smell to the reaction but the reaction caused gases to form. It took about 120 seconds for the reaction to end and it was evident by looking at the solution. It looked like a cloudy white liquid. In the Sodium hydrogen carbonate reaction there was extreme reaction in that a lot of bubbles formed therefore NaHCO3(s) powder had to be slowly poured inside the calorimeter.

Title: Raw data table of minimum and maximum temperature, mass and molar mass of Sodium Anhydrous Carbonate and Sodium hydrogen carbonate.
Name of Compound: | Formula: | Mass,m/g (±0.001g): | Molar Mass, Mr/gmol-1 | Initial Temperature (±0.01 °C) | Final Temperature (±0.01°C) |
Sodium Anhydrous Carbonate | Na2CO3(s) | 14.00 | 106.00 | 21.41 | 22.69 |
Sodium hydrogen carbonate | NaHCO3(s) | 8.00 | 84.00 | 20.23 | 11.52 |
Data Processing:

Endothermic reaction: NaHCO3(s) + HCl → NaCl(aq)+CO2(g)+ H2O

q = (100g) X (4.18Jg-1k-1) X (8.71K) /1000 = 3.64 kJ mol-1
Limiting reactant:
n=mass/ Mr
NaHCO3(s) =14g/ 84g=0.17mol of NaHCO3(s)
HCl= 100g/36g=2.78 mol of HCl
△H =3.64 /0.17= 21.41 kJ mol-1

Exothermic reaction: Na2CO3(s) + 2HCl → 2NaCl (aq) +CO2 (g) + H2O
q = (100g) X (4.18Jg-1k-1) X (1.28K) /1000= 0.54 kJ mol-1

Limiting reactant:
n=mass/ Mr
Na2CO3(s) =8g/106g=0.075 mol of Na2CO3(s)
HCl=100g/36g=2.78 mol of HCl
△H =0.54/0.075 =-7.13 kJ mol-1

Hess’s Law:
  1. NaHCO3(s)+ HCl → NaCl(aq)+CO2(g)+ H2O
Na2CO3(s) + 2HCl → 2NaCl (aq) +CO2 (g) + H2O

  2. (NaHCO3(s)+ HCl → NaCl(aq)+CO2(g)+ H2O)x2
-(Na2CO3(s) + 2HCl → 2NaCl(aq) +CO2(g)+ H2O)

  3. 2NaHCO3(s)+ 2HCl → 2NaCl(aq)+2CO2(g)+ 2H2O
2NaCl(aq) +CO2(g)+ H2O→ Na2CO3(s) + 2HCl...


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