In an experiment to determine the enthalpy change for this reaction, you combine 0.158 g of Mg metal with enough HCl to make 100.0 mL of solution in a coffee-cup calorimeter. The HCl is sufficiently concentrated so that the Mg completely reacts. The temperature of the solution rises from 25.6 °C to 32.8 °C as a result of the reaction. Find ΔHrxn for the reaction as written. Use 1.00 g/mL as the dens

Respuesta :

Answer:

The value of Δ [tex]H_{rxn}[/tex] for the reaction =  463 [tex]\frac{KJ}{mol}[/tex]

Explanation:

[tex]q_{rxn} = - q_{sol}[/tex]

[tex]q_{rxn} = H_{rxn}[/tex]

Δ [tex]H_{rxn}[/tex] = - [tex]q_{sol}[/tex] ------ (1)

We know that

[tex]q_{sol} = m c ( T_{2} - T_{1} )[/tex]

[tex]q_{sol} =[/tex] (1)(100) × 4.18 × (32.8 - 25.6)

[tex]q_{sol} =[/tex]  3010 J = 3.01 Kilo Joule

From equation (1)

Δ [tex]H_{rxn}[/tex]  = 3.01 Kilo Joule

No. of moles

[tex]N = \frac{m}{M}[/tex]

m = 0.158 gm & M = 24.31  gm Mg

No. of moles    

[tex]N = \frac{0.158}{24.31}[/tex]

N = 0.0065

Therefore

Δ [tex]H_{rxn}[/tex]  = [tex]\frac{3.01}{0.0065}[/tex]

Δ [tex]H_{rxn}[/tex]  =  463 [tex]\frac{KJ}{mol}[/tex]

This is the value of Δ [tex]H_{rxn}[/tex] for the reaction.