Workshop 6: Coffee Cup Calorimetry Calorimetry is the measurement of heat transf

Question

Workshop 6: Coffee Cup Calorimetry Calorimetry is the measurement of heat transfer. Devices that measure the amount of heat released or absorbed during a process are called calorimeters. Coffee cup calorimeter is the simplest calorimeter and is often used to measure the heats of chemical reactions at constant pressure (also called enthalpies). This calorimeter consists of a Styrofoam cup with a plastic lid and a thermometer In today's workshop we will use calorimetry to calculate the standard malar enthalpy of reaction or the enthalpy change that occurs in a system when 1 mole of matter is transformed by a chemical reaction at 1 atm: qrxn (in J/mol, at constant pressure and pV-work only), where q = crndT Let's consider the following chemical experiment: A student wants to measure the heat of neutralization reaction. To do this she mixed in a coffer cup calorimeter 35.0 mL of 0.70M HCl solution and 65.0 mL of 0.50M NaOH solution both at 22.0°C initially. She then continued to measure the temperature of the mixture for 10 minutes. 1. Write a chemical equation, a complete ionic and a net ionic equations for this reaction. Chemical equation: Complete ionic equation: Net ionic equation 2. Now discuss with your group the following questions: (a) What is(are) the product(s) of this reaction? (b) What is the system in this experiment and what are the surroundings? (c) Is this system an open one, a closed one or an isolated one? Before you write down your answers make sure that EVERYONE in your group can justify each them. Now write your answers below and don't forget to explain them. s(are) the product(s) in this reaction. (b) The system: The surroundings c) we can consider this system to be an em, because

Explanation / Answer

Solution:

1)

Complete reaction of given nuetralization reaction is

HCl + NaOH ----> NaCl + H2O (l)

Complete ionic eqauation is

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) ———> Na+(aq) + Cl-(aq) + H2O(l)

Net ionic equation

H+(aq) + OH-(aq) ———> H2O(l)

products of the reaction are NaCl and H2O

System is the Solution

Sorrounding is water produced by reaction

as coffee cup calorimeter is sorrounded by stryfoam no heat will be released to the atmoshpere

It is closed system as energy is not transferred from the system to the sorroundings in this simple coffe cup calorimeter.

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