# Molar enthelpy of combustion of magnesium

• domthebomb
In summary, the molar enthalpy of combustion of magnesium is the amount of heat released when one mole of magnesium undergoes complete combustion in excess oxygen, with a standard value of -601.8 kJ/mol. This value is negative because the reaction releases energy in the form of heat, due to the products having lower enthalpies than the reactants. It is measured using a bomb calorimeter and can be affected by factors such as purity, excess oxygen, and reaction conditions. In real-world applications, it is used in industries such as metallurgy and energy production, as well as in the development of new materials and fuels.
domthebomb

1. Homework Statement

In a calorimeter, a 1.0g sample of magnesium is burned to form MgO. In doing so, 25.5 kJ of energy is released. The molar enthalpy of combustion of magnesium is:

a) -0.0392 kJ/mol
b) -25.5 kL/mol
c) -306.2 kJ/mol
d) -620 kJ/mol

Q= mc DELTA t

## The Attempt at a Solution

2Mg + O2 --> 2MgO

... don't know where to start

PLEASE! i need help fast

If 1g of magnesium releases 25.5 kJ of energy when burnt, how much energy will be released when 1 mole will be burnt?

!

The molar enthalpy of combustion of magnesium can be calculated by dividing the energy released (25.5 kJ) by the number of moles of magnesium used (1.0 g/24.31 g/mol = 0.041 moles). This gives a value of -620 kJ/mol, which is option d) in the given choices. This means that for every mole of magnesium burned, 620 kJ of energy is released. The negative sign indicates that the reaction is exothermic, meaning it releases heat energy. The equation you provided, 2Mg + O2 --> 2MgO, is correct and can be used to calculate the molar enthalpy of combustion. Remember to use the correct units and convert if necessary. I hope this helps!

## What is the molar enthalpy of combustion of magnesium?

The molar enthalpy of combustion of magnesium is the amount of heat released when one mole of magnesium undergoes complete combustion in excess oxygen. It is represented by the symbol ΔHc and has a standard value of -601.8 kJ/mol.

## Why is the molar enthalpy of combustion of magnesium negative?

The molar enthalpy of combustion of magnesium is negative because the reaction releases energy in the form of heat. This is because the products of the reaction, magnesium oxide and carbon dioxide, have lower enthalpies than the reactants, magnesium and oxygen gas.

## How is the molar enthalpy of combustion of magnesium measured?

The molar enthalpy of combustion of magnesium can be measured using a bomb calorimeter, which is a device that allows for the complete combustion of a substance in a controlled environment. The heat released during the reaction is then measured and used to calculate the enthalpy of combustion.

## What factors can affect the molar enthalpy of combustion of magnesium?

The molar enthalpy of combustion of magnesium can be affected by factors such as the purity of the magnesium sample, the amount of excess oxygen present, and the temperature and pressure at which the reaction takes place. These factors can impact the accuracy of the measurement and should be controlled for in experiments.

## How is the molar enthalpy of combustion of magnesium used in real-world applications?

The molar enthalpy of combustion of magnesium is used in industries such as metallurgy and energy production, where magnesium is used as a fuel source. It is also used in the design and development of new materials and fuels, as well as in the study of thermodynamics and chemical reactions.

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