Enthelpy change of reaction with calorimeter

In summary, a student used a calorimeter with a heat capacity of 133.2 J/°C and filled it with 100.0 g of 25.00°C dilute HCl solution. They then added 0.496 g of Mg metal and the final temperature of the apparatus reached 41.37°C. The question asked for the enthalpy change for the reaction between Mg and HCl, and the solution was found by using the equation ΔH = -1714.9 J/mol.
  • #1
nicolodn
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Homework Statement


Student uses another calorimeter with a heat capacity of 133.2 J/°C. S/he fills the calorimeter with 100.0 g of 25.00°C dilute HCl solution and adds 0.496 g Mg metal (24.3 g/mol). The final temperature of the apparatus comes to 41.37°C.
What is the enthalpy change for the reaction as written?

Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g)

Take the specific heat capacity of the dilute acid solution as being equal to that of water, and neglect the heat capacity of the magnesium metal.

Hint: the heat evolved by the Mg reaction is gained by the water and calorimeter


Homework Equations





The Attempt at a Solution


m x C x T + c x T
 
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  • #2
= m x C x T 100 g HCl x 4.18 J/g°C x (41.37°C - 25°C) + 133.2 J/°C x (41.37°C - 25°C) = 0.496 g Mg x 24.3 g/mol x ΔH ΔH = -1714.9 J/mol
 

FAQ: Enthelpy change of reaction with calorimeter

How is enthalpy change of reaction measured with a calorimeter?

The enthalpy change of a reaction can be measured with a calorimeter by using the principle of energy conservation. The reaction is carried out in a sealed chamber within the calorimeter, and the heat released or absorbed by the reaction is transferred to the surrounding water in the calorimeter. The change in temperature of the water can then be used to calculate the enthalpy change of the reaction.

What is the purpose of using a calorimeter in measuring enthalpy change of reaction?

A calorimeter is used to measure enthalpy change of reaction because it provides a controlled environment where the heat released or absorbed by the reaction can be accurately measured. This allows for precise calculation of the enthalpy change of the reaction.

How does the heat capacity of the calorimeter affect the measurement of enthalpy change of reaction?

The heat capacity of the calorimeter, which is the amount of heat needed to raise the temperature of the calorimeter by 1 degree Celsius, can affect the measurement of enthalpy change of reaction. A higher heat capacity means that the calorimeter will absorb more heat from the reaction, resulting in a lower measured temperature change. This can lead to an underestimation of the enthalpy change of the reaction.

Can the enthalpy change of reaction be negative?

Yes, the enthalpy change of reaction can be negative. This indicates an exothermic reaction, where heat is released during the reaction. On the other hand, a positive enthalpy change of reaction indicates an endothermic reaction, where heat is absorbed during the reaction.

How can the enthalpy change of reaction be affected by the experimental conditions?

The enthalpy change of reaction can be affected by the experimental conditions such as the concentration of reactants, pressure, and temperature. Changing these conditions can alter the rate of reaction and ultimately affect the amount of heat released or absorbed, thus impacting the calculated enthalpy change of reaction.

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