Lab report experiment hess law PDF

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FACULTY OF APPLIED SCIENCELABORATORY REPORTPHYSICAL CHEMISTRYCHMNAME: AMIR AIMAN ANIQ BIN AHMAD RASHIDIID NO.:EXPERIMENT: 1TITLE: CALORIMETRY: HESS’S LAWDATE OF SUBMISSION: 11 / 11 / 2020OBJECTIVE To compare the heat capacities of the coffee cup calorimeter and a copper calorimeter To determine the ...

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FACULTY OF APPLIED SCIENCE LABORATORY REPORT PHYSICAL CHEMISTRY CHM432

NAME: AMIR AIMAN ANIQ BIN AHMAD RASHIDI ID NO.:2020449442 EXPERIMENT: 1 TITLE: CALORIMETRY: HESS’S LAW DATE OF SUBMISSION: 11 / 11 / 2020

OBJECTIVE 1. To compare the heat capacities of the coffee cup calorimeter and a copper calorimeter 2. To determine the standard enthalpy of formation of magnesium oxide, ∆H⁰f.

FLOWCHART OF METHODOLOGY APPARATUS: 1. 2. 3. 4. 5.

Thermometer (2) Styrofoam cup with cardboard cover lid (2) Copper calorimeter with insulating cover (1) 100 cmᶺ3 beaker 100 cmᶺ3 graduated cylinder

CHEMICAL: 1. 2.0 M hydrochloric acid 2. Magnesium oxide powder 3. Magnesium powder PPE (Personal Protective Equipment) Wear appropriate PPE: goggles, lab coat, proper shoes PROCEDURE A. HEAT CAPACITY OF CALORIMETER

Deliver 50 cm3 tap water into calorimeter by using burette

Replace thermometer and cover

Enter the lid and stir the water carefully with the thermometer

Using another thermometer, record temperature hot water and pour it into the calorimeter that contain cold water at 5 minutes.

Record the temperature every 15 seconds for the next 3 minutes.

Repeat step by using cooper calorimeter

Record the water temperature in 1 minute at 4 minutes intervals

Measure 50 cm3 hot water by using graduated cylinder and pour into beaker

B. MAGNESIUM WITH HYDROCHLORIC ACID

Weigh 1.0 – 1.1 g of magnesium powder

Record the exact weight

At five minute,pour quickly the magnesium powder into HCL

Record the temperature every 1 minutes for 4 minutes

Then,enter the lid and stir the contents in calorimeter,then replace the thermometer

Record the temperature next 3 minute at 15 minutes intervals

Drain 50 cm3 of 2 M HCl from burette to calorimeter

Then, replace the cover and thermometer

C. MAGNESIUM OXIDE WITH HYDROCHLORIC ACID

Weigh 1.6 -1.8 g magnesium oxide

Record the exactly weight

Repeat step 2 in Experiment B

D. HYDROGEN GAS WITH OXYGEN GAS

Tabulate all your results

Make necessary temperature-time plots to obtain the corrected temperature change.

Extrapolate the straight line of the graph to the fifth minutes

Compare the values and explain whether you would expect to get the same or different temperature change, (ΔT)

Calculate the heat capacity of both calorimeters

The difference between the temperatures at the fifth minute corresponds to the corrected temperature change.

Calculate the heats of reaction for reactions 2 and 3 in kJ /mol

Need to find out the moles of reactants involved in the reactions.

Calculate the percent error and discuss the factors that may have affected your result.

Compare the result you obtain with those from other group using the other type of calorimeter

Consult the literature to obtain the accepted value for the heat of formation of magnesium oxide

Discuss the factors that may have lead to the difference in values.

Show how chemical equations 2, 3, and 4 can be added to produce chemical equation 1

Show how the heats of reaction (kJ mol1 value) for reactions 2, 3, and 4 can be added to yield the heat of reaction for reaction 1.

RESULT DATA SHEET: TEMP. OF HOT WATER (⁰C) MASS OF Mg (g) MASS OF MgO (g) Coffee cup calorimeter Time T (⁰C)

Minute 1 Minute 2 Minute 3 Minute 4 15 Sec 30 Sec 45 Sec Minute 5 15 Sec 30 Sec 45 Sec Minute 6 15 Sec 30 Sec 45 Sec Minute 7

24.5 24.5 24.5 24.5 32.0 32.0 32.0 32.0 32.5 32.5 32.5 32.5 32.5 32 31.5 31.5

42 (coffee cup calorimeter) 45 (copper calorimeter) 1.0265 g 1.6589 g Cooper calorimeter

Mg and HCL

MgO and HCL

Time

T (⁰C)

Time

T (⁰C)

Time

T (⁰C)

Minute 1 Minute 2 Minute 3 Minute 4 15 Sec 30 Sec 45 Sec Minute 7 15 Sec 30 Sec 45 Sec Minute 6 15 Sec 30 Sec 45 Sec Minute 7

24.5 24.5 24.5 24.5 34.5 33.0 33.0 32.5 32.0 31.5 31.5 31.5 31.0 31.0 31.0 30.5

Minute 1 Minute 2 Minute 3 Minute 4 15 Sec 30 Sec 45 Sec Minute 5 15 Sec 30 Sec 45 Sec Minute 6 15 Sec 30 Sec 45 Sec Minute 7

24.5 24.5 24.5 24.5 26.0 45.0 54.0 54.5 56.0 62.5 63.0 63.5 63.5 63.5 63.5 63.5

Minute 1 Minute 2 Minute 3 Minute 4 15 Sec 30 Sec 45 Sec Minute 5 15 Sec 30 Sec 45 Sec Minute 6 15 Sec 30 Sec 45 Sec Minute 7

24.5 24.5 24.5 24.5 39.0 40.5 41.0 41.5 42.0 42.5 42.5 42.5 42.5 43.0 43.0 43.0

1.

Time Versus Temperature of Coffee Cup Calorimeter

2.

Time Versus Temperature of Copper Calorimeter

3.

Time Versus Temperature of Mg and HCl

4.

Time Versus Temperature of MgO and HCl

QUESTIONS 1.

a) Which of the two calorimeters: coffee cup calorimeter or copper calorimeter has higher specific heat capacity?  Coffee cup calorimeter has a higher heat capacity b) What conclusion can you make regarding the relationship of heat capacity of calorimeter with temperature change of the reactions?  The capacity of both calorimeters has different temperature change, this is because copper conducts heat much more effectively than coffee cup. The calorimeter will carry the heat away to the outside world faster than the coffee cup. The higher the heat capacity of the calorimeter, the higher the temperature change of the solution. 2. For the following problems, assume that the volume of the final solution is 200 cm3 , the density of the solution is 1.00 g mL1 and the heat capacity of the solution is the same as water (4.184 J g1 C). a) When 0.800 g of Ca metal is added to 200 cm3 of 0.500 M HCI (aq) according to the method described in Procedure B, a temperature increase of 13.0 C is observed. What is Hrxn at room temperature for the reaction of Ca(s) + 2H+ (aq)?  Ca(s) + 2HCl(aq) → CaCl₂ + H₂O Q = 𝒎𝒄∆𝑻 (0.800g)(4.184J/g°C)(85°C - 31°C) =0.181KJ Mole = 0.800g/40g/mol =0.02mol ∆H = Q/mol =0.181 KJ/0.02 mol =9.05 KJ/mol

b) When 1.12 g of CaO is added to 200 cm3 of 0.500 M HCI (aq) according to the method described in Procedure B, a temperature increase of 4.62 C is observed. What is Hrxn at room temperature for the reaction of CaO(s) + 2H+? 

CaO + HCl → CaCl₂ + H₂O ∆H = Q/mol (1.12g) (4.184 J/g°C) (76.62 °C - 31°C) =0.214kJ Mole =1.12g /640g/mol =1.75 * 10^-3 ∆H = Q/mol =0.214kJ/1.75 x 10-3 =122.29 kJ/mol

3. A student carelessly inserts the thermometer while assembling the coffee cup calorimeter and a large hole is torn in the plastic lid. How will this affect his experimental results? 

The large hole in the plastic lid will affect the experimental result, this is because the heat will release through the hole and effect the temperature reading.

DISCUSSION The heat capacity of both calorimeters is: (Q Cal for coffee cup calorimeter)

(Q CAL for cooper cup calorimeter)

Q hot= 𝑚𝑐∆𝑇

Q hot= 𝑚𝑐∆𝑇

=50g (4.18 J/g °C) (42 °C - 32°C)

=50g (4.18 J/g °C) (45°C – 34.5°C)

=2090 J

=2194.5 J

Q cold= 𝑚𝑐∆𝑇

Q cold= 𝑚𝑐∆𝑇

=50g (4.18 J/g °C) (32 °C – 24.5°C)

=50g (4.18 J/g °C) (34.5°C – 24.5°C)

=1567.5 J

=2090 J

Q hot = Q cold + Q cal

Q hot = Q cold + Q cal

2090 J = 1567.5 J + Q cal

2194.5 J = 2090 J + Q cal

Q cal = 2090 J – 1567.5 J

Q cal = 2194.5 J – 2090 J

= 522.5 J

= 104.5 J

Q cal = C cal (T f –T c)

Q cal = C cal (T f –T c)

522.5 J = C cal (32°C – 24.5°C)

104.5 J = C cal (34.5°C – 24.5°C)

C cal = 69.67 J/°C

C cal = 10.45 J/°C

The capacity of both calorimeters has different temperature change, this is because copper conducts heat much more effectively than coffee cup. The calorimeter will carry the heat away to the surrounding faster than the coffee cup.

The heat reaction for reaction 2 and 3 in kJ /mol. The moles of reactants involved in the reaction are: Chemical Equation: Mg + 2HCl → MgCl₂ +H₂ MgO + 2HCl → MgCl₂ 

Mg + MgO → H₂ + H₂O

Mol MgO = 1.6589 g / (24.3) (16) = 4.27 x 10-3 (limiting reactant) Q = 𝑚𝑐∆𝑇 = (1.0265 g) (4.18) (42 – 24.5) =75.088 J =0.07509 kJ ∆H rxn Mg = Q /mole =0.07509 kJ /4.27 x 10-3 =17.585 kJ/mol Q = 𝑚𝑐∆𝑇 = (1.6589 g) (4.18) (42 – 24.5) = 121.35 J = 0.1214 kJ ∆H rxn Mg = Q /mole = 0.1214 kJ /4.27 x 10-3 mol = 28.431 kJ/mol

Chemical equations 2,3,4 can be added to produce chemical equation 1: Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g) ------② MgO (s) + 2HCl (l) → MgCl₂ (aq) + H₂O (l) ------③ H₂ (g) + ½ O₂ → H₂O (l) ------④

Solution: Mg(s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g) ------② MgCl₂(aq) + H ₂O(l) → MgO(s) + 2HCl(l) ------③ H₂(g) + ½ O₂ → H₂O(l) ------④ Mg(s) + ½ O₂ → MgO(s) ------①

The heat of reaction (kJ /mol value) for reactions 2,3 and 4 can be added to yield the heat reaction for reaction 1. ∆H = 𝒎𝒄∆𝑻 (Mg and HCl coffee cup calorimeter) = (1.0265 g) (69.67 J/°C) (42°C – 24.5°C) =1251.53 J = 1.2515 kJ Mole Mg = 1.0265 g / 24.31g/mol = 0.0422 mol = 1.2515 kJ / 0.0422 mol =29.656 kJ/mol

∆H = 𝒎𝒄∆𝑻 (MgO and HCl coffee cup calorimeter) = (1.6589 g) (69.67 J/°C) (39°C – 24.5°C) = 1675.85 J =1.6759 kJ Mole MgO = 1.6589 g / 40.30 g/mol = 0.0412 mol =1.6759 kJ / 0.0412 mol =40.677 kJ/mol

∆H = 𝒎𝒄∆𝑻 (Hydrogen) = -285.8 KJ/mol

Chemical equations 2,3,4 can be added to produce chemical equation 1: Mg(s) + 2HCl (aq) → MgCl ₂(aq) + H₂(g) ------②

∆H = -29.656 kJ/mol

MgO(s) + 2HCl(l) → MgCl ₂(aq) + H₂O) ------③

∆H = -40.677 kJ/mol

H₂(g) + ½ O₂ → H₂O(l) ------④

∆H = -286 kJ/mol

Solution: Mg(s) + 2HCl (aq) → MgCl₂(aq) + H₂(g) ------②

∆H = -29.656 kJ/mol

MgCl₂(aq) + H₂O(l) → MgO(s) + 2HCl(l) ------③

∆H = + 40.677 kJ/mol

H₂(g) + ½ O₂ → H₂O(l) ------④

∆H = -286 kJ/mol

Mg(s) + ½ O₂ → MgO(s) ------① ∆H rxn = -29.656 kJ/mol + 40.677 kJ/mol + (-286 kJ/mol) = -274.979 kJ/mol Based on the calculation, the standard enthalpy formation of magnesium oxide is - 274.979 kJ/mol.

The theoretical value of enthalpy formation of MgO is -601.8 KJ/mol Percent error = (actual value/theoretical value) x 100 = (-274.979 kJ/mol /-601.8 kJ/mol) x 100 = 45.69%

CONCLUSION This experiment is conducted to compare the heat capacities of a coffee cup calorimeter and a copper calorimeter which is found to be 1567.5 J and 2090 J respectively. The standard enthalpy of formation of magnesium oxide, ΔHºf also can be determined during this experiment. The ΔHºf of magnesium oxide is found to be - 274.979 kJ/mol. Thus, the objectives of this experiment are successfully achieved...