• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# experiment Hess Law

Extracts from this document...

Introduction

Name : Mohd Haziq Al-Hakim Bin Hamirruddin Class : M08F Date : 9 July 2009 Practical : 16 Data Collection and Processing Part A:- Mass of magnesium ribbon = 0.2836 � 0.0001g Volume of 0.5 M of HCl = 50.0 � 0.5 cm3 Reactant Initial Temperature, � 0.5�C Highest Temperature, � 0.5�C Mg + HCl 27.0 40.5 Table 1 shows the initial and highest temperature for reaction between Mg and HCl To calculate the change in temperature, the following equation will be used:- Reactant Change in Temperature, � 1.0�C Mg + HCl 13.5 Table 2 shows the change in temperature for reaction between Mg and HCl Equation for part A:- Mg (s) + 2HCl (aq) --> MgCl2 (aq) + H2 (g) Mole of magnesium Mole of hydrochloric acid = mass = MV RMM 1000 = 0.2836 g = 50.0x0.5 24.3 1000 = 0.0118 mol = 0.025 mol Thus, ...read more.

Middle

30.0 Table 3 shows the initial and highest temperature for reaction between MgO and HCl To calculate the change in temperature, the following equation will be used:- Reactant Change in Temperature, � 1.0�C MgO + HCl 2.0 Table 4 shows the change in temperature for reaction between MgO and HCl Equation for part B:- MgO (s) + 2HCl (aq) --> MgCl2 (aq) + H2O (l) Mole of magnesium oxide Mole of Hydrochloric acid = mass = MV RMM 1000 = 0.4985g = 50x0.5 (24.3+16) 1000 = 0.0124 mol = 0.025 mol Thus, the limiting reagent is magnesium oxide Calculation: Heat change, Q = mc?T = 50g � 4.2 Jmol-1�C-1 � 2 �C = 420 J ?Hrxn = -420_ 0.0124 = -33.87 kJmol-1 Uncertainties: Mass = = 1.0 % Temperature = = 50.0 % No of mole = = 8.1% Total = 59.1% ?Hrxn = -33.87 kJmol-1 � 59.1 % Since the reactions are exothermic, the ?Hrxn for each reaction is negative. ...read more.

Conclusion

+ 2HCl(aq) � MgCl2(aq) + H2(g) ?Hrxn = -240.25 kJmol-1 � 9.25% MgCl2(aq) + H2O(l) � MgO(s) + 2HCl(aq) ?Hrxn = +33.87 kJmol-1 � 59.1% Mg(s) + H2O(l) � MgO(s) + H2(g) ?Hrxn = -206.38 kJmol-1 � 68.35% ?Hrxn = -206.38 kJmol-1 � 16.12 % For the theoretical value: 1. Mg(s) + (g) MgO(s) ?Hrxn = -601.8 kJmol-1 2. H2(g) + (g) H2O(l) ?Hrxn = -285.8 kJmol-1 By reversing equation 2: 3. H2O(l) H2(g) + (g) ?Hrxn = +285.8 kJmol-1 The theoretical value of the reaction, equation 1 + equation 3: Mg(s) + (g) MgO(s) ?Hrxn = -601.8 kJmol-1 H2O(l) H2(g) + (g) ?Hrxn = +285.8 kJmol-1 Mg(s) + H2O(l) MgO(s) + H2(g) ?Hrxn = -316.0 kJmol -1 ?Hrxn obtained from this experiment = -206.38 kJmol-1 The theoretical value of ?Hrxn = -316.0 kJmol -1 Percentage error = Theoretical value - Experimental value Theoretical value = = 34.69% Reference: Chemistry: A Central Science by Brown, Le May and Bursten ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Chemistry section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related International Baccalaureate Chemistry essays

1. ## Experiment - The Empirical Formula of Magnesium Oxide

As shown on the graph, R2 (the correlation coefficient) equals to 0.5751, indicating that the data was not very reliable since the value was away from 1. In addition, the data points did not spread out, i.e., they were gathering at 0.004 to 0.006 moles. Consequently, the gradient was influenced.

2. ## Hess's Law. The experiment conducted was meant to determine the enthalpy of formation of ...

+ 1/2O2(g) --> MgO(s) - 601.6 kJ/mol 10.5% Ca(s) + 1/2O2(g) --> CaO(s) - 635.5 kJ/mol 48.5% Notes: * Percent error was calculated using the following formula: % Error = (|accepted value - experimental value|) ������������������������������� x 100% accepted value Ex: Mg(s) + 1/2O2(g) --> MgO(s) : % Error = (|accepted value - experimental value|)

1. ## Hesss Law Lab, use Hesss law to find the enthalpy change of combustion of ...

Temp.0C (�0.50C ) HCl 0 21 30 21 60 21 90 21 120 21 150 21 180 21 HCl+MgO 190 21 200 21 210 22 220 22 230 23 240 23 250 24 260 24 270 24 280 25 290 25 300 26 330 26 360 25 390 25 420 24 450 24 480 24 EXPERIMENT 2 C time/s(�1sec)

2. ## Lab Experiment : The change in mass when magnesium burns. (Finding the empirical formula ...

8. Less flame. 9. No flame but it glows. 10. Less sparks and less glow. 11.Little smoke. 12.No smoke(white fluid material and residue on lid). 13. No further reaction. Raw Data: Initial mass of crucible with lid ( in grams) + 0.0001= 27.6400g Mass of magnesium inside crucible with the lid ( in grams)

1. ## Confirming Hess's Law Experiment

final percent error of 16.4% relative to the percent error of Trial #2, which was 17.6%. The rubber stopper is able to trap the heat and pressure within the calorimeter which is essential when calculating molar enthalpy. The third and final intermediate reaction involving the formation of water could not

2. ## The aim of this experiment is to examine the enthalpy of combustion of the ...

= m (CH3OH)M (CH3OH) = 1.50 g88.17 g mol-1 = 0.0170mol The enthalpy of combustion of methanol from here is : ?Hc (CH3OH) = Heat energy transformed to the waterAmount of methanol burnt = 10.24kJ0.0170mol ?Hc (CH3OH) = - 602.35kJ mol-1 Conclusion The hypothesis was the greater the number of

1. ## To determine the standard enthalpy of formation of Magnesium Oxide using Hess Law.

also reversed because the amount of heat required to form the reactants back from the products will be the same as the amount of heat given out when the reactants formed the product (in this case, the exothermic neutralization reaction of MgO and HCl).

2. ## Discovering the formula of MgO

The bright flame of MgO is very hard to extinguish and it emits a harmful intensity of UV light therefore do not look at the burning Mg for prolonged periods of time and wear eye protection. 3. Hot apparatus could be a hazard, it can cause skin damage therefore • Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to 