Heather is measuring the enthalpy change associated with reaction of magnesium w

Question

Heather is measuring the enthalpy change associated with reaction of magnesium with aqueous hydrochloric acid. She records the following in her laboratory notebook:

Assuming the density 1.00 M HCl is identical to that of pure water (1.00 g/mL) and that the specific heat capacity of the solution is identical to that of liquid water (4.184 J/g-K), what is the enthalpy change associated with the reaction, in units of J? Report your response to two digits after the decimal. Note: Do not use units (i.e. J) in your answer and don't forget to use a negative sign (-) before type your answer in number.with no-space in between (i.e. -3125.20).

mass Mg (g) 0.181 volume (mL) 1.00 M HCl 129.54 initial T of solution (oC) 18.13 final T of solution (oC) 29.41

Explanation / Answer

Density of HCl = Density of Water = 1.00 g/mL = Mass of HCl/Volume of HCl

Mass of HCl = 129.54 mL * 1.00 g/mL = 129.54 grams

Enthalpy evolved in the reaction = mass * specific heat capacity * change in temperature

=> -129.54 g * 4.184 J/gC * (29.41 - 18.13)

=> -6113.70 Joules

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