Question

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 molar 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: AI . qnn (in '/mol, at constant pressure and pV-work only), where q-cmaT 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 41.0 mL of 0.65M HBr solution and 52.0 mL of 0.38M KOH 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 equati 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. (a) is(are) the product(s) in this reaction (b) The system: The surroundings: General Ch mistry (c) We can consider this system to be an, system, because

Answer 1

ans)

from above data that

1. HBr+ KOH

Ionic equation : H+(aq) + Br-(aq) + k+(aq) + OH-(aq) --> k+(aq) + Br-(aq) + H2O(l)

net-ionic equation : H+(aq) + OH-(aq) --> H2O(l)

2. (a) Products for the reaction : KBr, H2O

(b) System is HBr + KOH

surrounding : calorimeter

(c) This can be considered as an isolated sytem because the heat lost or gained remained inside the calorimeter itself.