How much heat is gained (in Joules) by the water (qwater) when a chemical reaction takes place in...

Question:

How much heat is gained (in Joules) by the water (qwater) when a chemical reaction takes place in 100.0 mL aqueous solution and has a temperature increase of {eq}13.26^{\circ}C {/eq}? (Remember cwater = 4.180 {eq}J/ ^{\circ}Cg {/eq})

Heat Transfer:

In calorimetry experiments, we observe the heat exchange between solutions and possible chemical reactions. We assume in a calorimeter that there is no heat loss to the surroundings when we contain a reaction in a calorimeter. Thus, the heat is transferred only to the calorimeter, which makes it easier to determine certain properties of a reaction.

Answer and Explanation:

Determine the heat absorbed by water, {eq}\displaystyle q_{water} {/eq}, by applying the equation, {eq}\displaystyle q = mc\Delta T {/eq}, where {eq}\displaystyle m {/eq} is the mass, {eq}\displaystyle c = 4.186\ \rm{J/g ^\circ C} {/eq} is the specific heat of water, and {eq}\displaystyle \Delta T = 13.26 ^\circ C {/eq} is the corresponding change in the temperature. We determine the mass of water by multiplyting the volume, {eq}\displaystyle V = 100.0\ mL {/eq}, to the density of pure wwater, {eq}\displaystyle \rho = 1.0\ \rm{g/mL} {/eq}, or {eq}\displaystyle m = 100.0\ mL\times 1.0\ g/mL = 100\ g {/eq}. Thus, we proceed with the solution.

{eq}\begin{align} \displaystyle q &= mc\Delta T\\ &= 100\ g\times 4.186\ \rm{J/g ^\circ C}\times 13.26 ^\circ C\\ &\approx 5550\ J \end{align} {/eq}


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Thermal Expansion & Heat Transfer

from High School Physics: Help and Review

Chapter 17 / Lesson 12
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