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Chem Ia

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Submitted By weien
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CHEM IA 11
Aim
To determine the enthalpy change of reaction between zinc powder and aqueous copper(II) ions
Uncertainties of Apparatus Electronic balance | ±0.001g | 50cm3 measuring cylinder | ± 0.5cm3 | Thermometer | ± 0.1oC | Digital stopwatch | ± 0.2s |

Mass/g of zinc in weighing bottle measured by electronic balance for Method 1 Mass of Zn (±0.002) / g | 0.9123 | Mass of weighing bottle (± 0.001) / g | 3.5840 | Mass of Zn + weighing bottle ( ±0.001) /g | 4.4963 |

Highest temperature recorded after adding Zn to copper (II) sulfate solution for Method 1 Initial temperature (±0.1) / ⁰C | 22.0 | Highest temperature (±0.1) / ⁰C | 31.5 | Temperature change (±0.2) / ⁰C | 8.50 |

Mass/g of zinc in weighing bottle measured by electronic balance for Method 2 Mass of Zn (±0.002) / g | 0.9123 | Mass of weighing bottle (± 0.001) / g | 3.5840 | Mass of Zn + weighing bottle ( ±0.001) /g | 4.4963 |

Temperature recorded before and after adding Zn is added to copper (II) sulfate for Method 2

Time (±0.2) / s | Temperature (±0.1) / ⁰C | 0.0 | 22.0 | 15.0 | 22.0 | 30.0 | 22.0 | 45.0 | 22.0 | 60.0 | 22.0 | 75.0 | 21.5 | 90.0 | 21.5 | 105.0 | 21.3 | 120.0 | 21.2 | 135.0 | 21.2 | 150.0 | 21.0 | 165.0 | 21.0 | 180.0 | 21.0 | 195.0 | 21.0 | 210.0 | 23.0 | 225.0 | 23.8 | 240.0 | 24.5 | 255.0 | 25.2 | 270.0 | 26.4 | 285.0 | 28.2 | 300.0 | 29.1 | 315.0 | 29.8 | 330.0 | 31.1 | 345.0 | 31.5 |

(Highest Temperature observed here)
(Highest Temperature observed here)

360 | 31.0 | 375.0 | 30.5 | 390.0 | 30.2 | 405.0 | 30.1 | 420.0 | 30.1 | 435.0 | 30.0 | 450.0 | 29.2 | 465.0 | 29.0 | 480.0 | 29.0 | 495.0 | 28.8 | 510.0 | 28.8 | 525.0 | 28.8 | 540.0 | 28.6 | 555.0 | 28.6 | 570.0 | 28.4 | 585.0 | 28.2 | 600.0 | 28.2 | 615.0 | 28.0 | 630.0 | 27.0 | 645.0 | 26.5 |

Data Processing
(Method 1) Calculation | Error Propagation | Mass of zinc 0.9123 (4sf)Mols of zinc=0.912365.37= 0.0139 (4sf)Volume of copper sulfate solution = 50.0cm3 (3sf)Mass of copper sulfate solution= 50.0g (3sf)Temperature change = 8.5oC (2sf)Enthalpy change of reaction = 50.0 x 4.3 x 8.50.0139= -131474 J mol-1 | ±%∆Mass=±0.0020.9123×100% =±0.2192%±%∆ Mols = =±0.2192%±%∆ Volume = ±0.550.0×100% = ±1.00%±%∆ Mass = = ±1.00% ±%∆ Temperature change = ±0.28.5×100% =±2.35%±%∆ Enthalpy change = ±(0.2192 +1.00 +2.35)%=±3.57% |

The heat of neutralisation is first produced when zinc is added to copper (II) sulphate solution, causing temperature to rise initially, subsequently it would drop, then finally rise to its maximum temperature.
To determine the highest temperature, we had to wait 5 minutes after the reaction had obtained its highest temperature. Afterwards, if it does not increase, it can be dedueced that that is the highest temperature.
In this experiment, Zinc was used in excess. This is observed after the experiment, when the black residue was left unreacted, being Zinc, Absence of pink residue indicates that copper (II) has been fully reacted.

A graph of temperature/⁰C against time/s is shown below

Method 2: Calculation | Error Propagation | Mass of zinc 0.9123 (4sf)Mols of zinc=0.912365.37= 0.0139 (4sf)Volume of copper sulfate solution = 50.0cm3 (3sf)Mass of copper sulfate solution= 50.0g (3sf)ΔH = (mcΔT)/n = (50.0x(4.3/1000)x-8.5)/(0.9123) = -1.667 kJ mol-1 (2sf) | ±%∆Mass=±0.0020.9123×100% =±0.2192%±%∆ Mols = =±0.2192%±%∆ Volume = ±0.550.0×100% = ±1.00%±%∆ Mass = = ±1.00% |

Limitations to the experiment 1. The zinc particles may form lumps, hence decreasing the exposed surface area and decreasing the reactivity of the zinc. Furthermore, a layer of copper would cover the zinc, impeding the reaction and slowing it down, therefore affecting all the results obtained from the experiment. 2. There could be possible heat that was lost to the surrounding, hence the temperature recorded may be inaccurate 3. The amount of zinc powder used was insufficient and the reaction is thus incomplete

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