Pre-Lab Assignment: Heat of Combustion-Magnesium (Show work for All Problems) Us

Question

Pre-Lab Assignment: Heat of Combustion-Magnesium (Show work for All Problems) Using the data below and using a value of 3.93 J/e'C as the specific heat of the solution (as in the pre lab lecture) and a value of 1.02 g/mL as the density of the reaction solution, questions that follow the data. answer the Magnesium/HCI Reaction 100.0 ml mL of solution Grams of Magnesiunm Final Temperature Initial Temperature At 0.244 32.2 C 21.3 C "C 10.9 Magnesium Oxide/HCI Reaction 1010ml mL of solution Grams of MgO Final Temperature Initial Temperature At 0.996 g 28.8C 214C 1. Calculate q (heat) for the Mg/HCI reaction in units of kl. Calculate AH in units of kJ/mole of Mg. (HINT: First calculate the mass of the solution) HEM 133, Lab Manual, Suffolk County Community College, Michael J. Grant Campus, NY Page 7

Explanation / Answer

Ans. #1. Mass of solution = Volume of solution x Density

                                                = 100.0 mL x (1.02 g / mL)

                                                = 102.0 g

# Heat gained by a solution is given by-

q = m s dT                            - equation 1

Where,

q = heat gained

m = mass

s = specific heat

dT = Final temperature – Initial temperature

Putting the values in equation 1-

q = 102.0 g x (3.93 J g-1 0C-1) x 10.90C

Or, q = 4369.374 J

# The total amount of heat gained by the solution to increase its temperature must be equal to the total amount of heat released during the reaction between Mg and HCl.

So,

            Heat released during reaction between Mg and HCl = - 4369.374 J

Note: the –ve sign indicates that heat is being released during the reaction.

# Given, Mass of Mg = 0.244 g

Moles of Mg = Mass / Molar mass

                        = 0.244 g / (24.305 g/ mol)

                        = 0.0100 mol

# Now,

            dH = Amount of heat released / Moles of Mg reacted

            Or, dH = -4369.374 J / 0.0100 mol

            Or, dH = -436937.4 J/ mol

            Hence, dH = -439.94 kJ/ mol

Hence, dH for the reaction = -439.94 kJ/ mol

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.