a) How this experiment is an illustration of Hess's Law? b) If you were to repeat this experiment in the “real world”, what are some of the major sources of error that could occur?

Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
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a) How this experiment is an illustration of Hess's Law?

b) If you were to repeat this experiment in the “real world”, what are some of the major sources of error that could occur?

PROCEDURE
HEAT OF REACTION (simulation)
Reaction 1
In this experimental simulation you will determine and compare the quantity of heat energy
released in three exothermic chemical reactions.
a. In the glassware menu, take out a 50 mL graduated cylinder and a foam cup. From tools
menu, take out the scale. From the chemical stockroom, move the distilled water and solid
NaOH onto the workbench.
Reaction 1: solid sodium hydroxide dissolves in water to form an aqueous solution of ions
b. Transfer 50.0 mL of water to the foam cup. To do this, drag the carboy of water onto the
graduated cylinder. Before you release the mouse button, the cursor will show a "plus sign" to
indicate that it is the recipient. A transfer text bar will appear, enter "50.0" (mL) and click on
pour. You will notice that the graduated cylinder reeds 50.0 mL
NaOH(s) → Na*(aq) + OH (aq) + X¡ kJ (DH9olution)
Reaction 2: Sodium hydroxide reacts with an aqueous solution of hydrogen chloride to form
water and an aqueous solution of sodium chloride.
c. Weigh about 1 gram of solid sodium hydroxide pellets, NaOH (s), directly into the foam Cup
and record its mass to the nearest 0.01 gram. To do this place the foam Cup on the balance so it
registers a mass, then click the "Tare" button. Drag the NaOH bottle onto the foam Cup. When
you release the mouse, the bottle will be tipped to show that it is in pour mode. Next type "1.00"
(grams) into the transfer bar and click pour. Note that the balance now reads the mass of the
transferred NaOH. Record this mass in your table. You may not take the Cup off the scale and
remove the scale from the workbench.
NaOH(s) + H*(aq) + Cl'(aq) → H2O(1) + Na*(aq) + CI(aq) + X, kJ (DHreaction)
Reaction 3: An aqueous solution of sodium hydroxide reacts with an aqueous solution of
hydrogen chloride
form wa
and an aqueous solution of sodium chloride.
Na" (aq) + OH (aq) + H*(aq) + Cl'(aq) → H2O(1) + Na*(aq) + Cl'(aq) + X3 kJ (DHneutralization)
In order to accurately measure the heat released in each reaction, we will be using a calorimeter.
For this experiment a Styrofoam Cup will act as a calorimeter. The change in temperature that
occurs for each reaction will be used to calculate the energy released in kilo joules per mole of
sodium hydroxide used (kJ/mol). We can assume for our calculations that any heat transferred to
the Styrofoam cup and surrounding air will be negligible. We can also assume that the specific
heat of water is 4.18 J/g°C
d. Click on the graduated cylinder, record its temperature and then drag it onto the foam Cup.
When you release the mouse, the graduated cylinder will be tipped to show that it is in pour
mode. Enter “50.0" (mL) in the transfer bar and then click pour. Record the highest temperature.
Reaction 2
a. Take 0.5 M HCl from the strong acid cabinet and foam Cup, and a 50mL graduated cylinder
from the glassware menu and place them on the workbench. The procedure for reaction 2 is
the same as for reaction 1 except that 50.0 mL of 0.50 M hydrochloric acid solution is used in
place of the water. After measuring 50.0 mL of HCl solution into the graduated cylinder,
proceed as before with steps (b) through to (d) of the procedure.
Reaction 3
a. Take out another graduated cylinder, a fresh foam Cup, the 1.0 M HCl and the 1.0M M
NaOH. (If you are running out of room, you may remove the previous chemicals from
workbench.) Measure 25.0 mL of 1.0 M HCl solution into a foam Cup. Pour an equal
volume of 1.0 M NAOH in the clean graduated cylinder.
b. Record the temperature of each solution to the nearest 0.1°C. Pour the sodium hydroxide
solution into the foam Cup and record the highest temperature obtained during the
reaction.
Transcribed Image Text:PROCEDURE HEAT OF REACTION (simulation) Reaction 1 In this experimental simulation you will determine and compare the quantity of heat energy released in three exothermic chemical reactions. a. In the glassware menu, take out a 50 mL graduated cylinder and a foam cup. From tools menu, take out the scale. From the chemical stockroom, move the distilled water and solid NaOH onto the workbench. Reaction 1: solid sodium hydroxide dissolves in water to form an aqueous solution of ions b. Transfer 50.0 mL of water to the foam cup. To do this, drag the carboy of water onto the graduated cylinder. Before you release the mouse button, the cursor will show a "plus sign" to indicate that it is the recipient. A transfer text bar will appear, enter "50.0" (mL) and click on pour. You will notice that the graduated cylinder reeds 50.0 mL NaOH(s) → Na*(aq) + OH (aq) + X¡ kJ (DH9olution) Reaction 2: Sodium hydroxide reacts with an aqueous solution of hydrogen chloride to form water and an aqueous solution of sodium chloride. c. Weigh about 1 gram of solid sodium hydroxide pellets, NaOH (s), directly into the foam Cup and record its mass to the nearest 0.01 gram. To do this place the foam Cup on the balance so it registers a mass, then click the "Tare" button. Drag the NaOH bottle onto the foam Cup. When you release the mouse, the bottle will be tipped to show that it is in pour mode. Next type "1.00" (grams) into the transfer bar and click pour. Note that the balance now reads the mass of the transferred NaOH. Record this mass in your table. You may not take the Cup off the scale and remove the scale from the workbench. NaOH(s) + H*(aq) + Cl'(aq) → H2O(1) + Na*(aq) + CI(aq) + X, kJ (DHreaction) Reaction 3: An aqueous solution of sodium hydroxide reacts with an aqueous solution of hydrogen chloride form wa and an aqueous solution of sodium chloride. Na" (aq) + OH (aq) + H*(aq) + Cl'(aq) → H2O(1) + Na*(aq) + Cl'(aq) + X3 kJ (DHneutralization) In order to accurately measure the heat released in each reaction, we will be using a calorimeter. For this experiment a Styrofoam Cup will act as a calorimeter. The change in temperature that occurs for each reaction will be used to calculate the energy released in kilo joules per mole of sodium hydroxide used (kJ/mol). We can assume for our calculations that any heat transferred to the Styrofoam cup and surrounding air will be negligible. We can also assume that the specific heat of water is 4.18 J/g°C d. Click on the graduated cylinder, record its temperature and then drag it onto the foam Cup. When you release the mouse, the graduated cylinder will be tipped to show that it is in pour mode. Enter “50.0" (mL) in the transfer bar and then click pour. Record the highest temperature. Reaction 2 a. Take 0.5 M HCl from the strong acid cabinet and foam Cup, and a 50mL graduated cylinder from the glassware menu and place them on the workbench. The procedure for reaction 2 is the same as for reaction 1 except that 50.0 mL of 0.50 M hydrochloric acid solution is used in place of the water. After measuring 50.0 mL of HCl solution into the graduated cylinder, proceed as before with steps (b) through to (d) of the procedure. Reaction 3 a. Take out another graduated cylinder, a fresh foam Cup, the 1.0 M HCl and the 1.0M M NaOH. (If you are running out of room, you may remove the previous chemicals from workbench.) Measure 25.0 mL of 1.0 M HCl solution into a foam Cup. Pour an equal volume of 1.0 M NAOH in the clean graduated cylinder. b. Record the temperature of each solution to the nearest 0.1°C. Pour the sodium hydroxide solution into the foam Cup and record the highest temperature obtained during the reaction.
Results
Reaction
1
2
3
Mass of NaOH
1.00 g
1.00 g
Volume of NaOH +
50.0 mL
50.0 mL
25.0 mL
HCl or H2O
Mass of solution
51.0 g
51.0 g
50.0 g
Initial Temperature
Final Temperature
25.00 •C
25.00 •C
25.00 •C
30.30 •C
36.97 •C
31.7 °C
ΔΤ
30.30 – 25.00
36.97 – 25.0
31.7 – 25.00
= 5.30 •C
11.97 C
= 6.7 °C
%3D
51.0 g * 4.18 * 5.30
= 1129 j/ 1.129 kJ
51.0 g * 4.18 * 11.97
= -2500 j/ -2.5 kJ
50.0 g * 4.18 * 6.7
= -1400.3 j / -1.4 kJ
0.025 mol
Heat of reaction
Mol NaOH
0.025 mol
0.0250 mol
Enthalpy, kJ/mol
1.129/0.025
-2.5/0.025
-1.4/0.025
-45 kJ/mol
= -100.0 kJ/mol
= -56.0 kJ/mol
Transcribed Image Text:Results Reaction 1 2 3 Mass of NaOH 1.00 g 1.00 g Volume of NaOH + 50.0 mL 50.0 mL 25.0 mL HCl or H2O Mass of solution 51.0 g 51.0 g 50.0 g Initial Temperature Final Temperature 25.00 •C 25.00 •C 25.00 •C 30.30 •C 36.97 •C 31.7 °C ΔΤ 30.30 – 25.00 36.97 – 25.0 31.7 – 25.00 = 5.30 •C 11.97 C = 6.7 °C %3D 51.0 g * 4.18 * 5.30 = 1129 j/ 1.129 kJ 51.0 g * 4.18 * 11.97 = -2500 j/ -2.5 kJ 50.0 g * 4.18 * 6.7 = -1400.3 j / -1.4 kJ 0.025 mol Heat of reaction Mol NaOH 0.025 mol 0.0250 mol Enthalpy, kJ/mol 1.129/0.025 -2.5/0.025 -1.4/0.025 -45 kJ/mol = -100.0 kJ/mol = -56.0 kJ/mol
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