Zn(s)+2HCl(aq)?ZnCl2(aq)+H2(g) Part A Find ? H rxn for this reaction as written.

Question

Zn(s)+2HCl(aq)?ZnCl2(aq)+H2(g)

Part A

Find ?Hrxn for this reaction as written. (Use 1.0 g/mL for the density of the solution and 4.18 J/g??C as the specific heat capacity.)

Zinc metal reacts with hydrochloric acid according to the following balanced equation.

Zn(s)+2HCl(aq)?ZnCl2(aq)+H2(g)

When 0.128g of Zn(s) is combined with enough HCl to make 52.4mL of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 22.0?C to 24.2?C.

Part A

Find ?Hrxn for this reaction as written. (Use 1.0 g/mL for the density of the solution and 4.18 J/g??C as the specific heat capacity.)

?Hrxn =   kJ/mol  

Explanation / Answer

Lets take a look

q = m *c * ?T

First we need to find the total mass and we are given Density

D = M / V

M = V * D

M = 1.0g/ml * 52.4ml =

M = 52.4grams

So now we find Q

Q= 52.4grams *( 4.18J/g *Celsius) * (24.2 - 22)
Q= 481.87 J

So now we need the moles Zn
0.128gZn / (1mol / 65.38 g Zn) = 0.0019578 mol Zn


?H(rxn) = 481.87J / (0.0019578 mol Zn)
= 246130.161J/mol
= 246.13Kj / mol

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