Question

5) Suppose you place 0.500 g of Mg metal in a coffee cup calorimeter.You add 100.0 mL of 1.00 M HCl.The mass of the HCl solution is 100.112 g.The reaction that occurs is as follows:

Mg (s) + 2 HCl (aq) ® MgCl₂ (aq) + H₂ (g)

The initial temperature of the HCl solution is 22.2°C and the final temperature after the reaction is complete is 44.8°C. The specific heat of water is 4.184 J/g·K, and magnesium is the limiting reactant.

a. How much heat is given off (generated) in this reaction?

b. What is the enthalpy change (DH) for the reaction per mole of magnesium?

6) A 2.358 g sample containing iron(II) is titrated using the standardized solution from question 5.If the titration requires 33.55 mL of titrant to reach the endpoint, what is the mass percent of iron in the sample?

Answer 1

(a)

Mass of Mg = 0.500 g.

The mass of the HCl solution is 100.112 g

Total mass

The initial temperature of the HCl solution is 22.2°C and the final temperature after the reaction is complete is 44.8°C. The temperature change

The specific heat (S) of water is 4.184 J/g·K or 4.184 J/g·°C

The amount of heat is given off (generated) in this reaction

(b)

Mass of Mg = 0.500 g.

The molar mass of Mg = 24.3 g/mol

The number of moles of Mg

The enthalpy change (DH) for the reaction per mole of magnesium is

Convert the unit into kJ/mol