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Why absolute value of enthalpy of system cannot be measured?
The absolute value of enthalpy cannot be measured because enthalpy is a state function, which means its value depends on the initial and final states rather than the absolute value. Only changes in enthalpy can be measured experimentally through processes like calorimetry.
How do you calculate the enthalpy of a reaction?
To calculate the enthalpy of a reaction, you subtract the sum of the enthalpies of the reactants from the sum of the enthalpies of the products. This is known as the enthalpy change (H) of the reaction. The enthalpy values can be found in tables or measured experimentally using calorimetry.
What is dimension of enthalpy?
The correct dimensional formula of latent heat is MoL2T2.
What unit is enthalpy change measured in?
Enthalpy change is measured in joules (J) or kilojoules (kJ). In some contexts, especially in chemistry, it may also be expressed in calories (cal) or kilocalories (kcal). The choice of unit typically depends on the scale of the reaction or process being studied.
How is Hess and law used to measure enthalpy of a desired reaction?
Hess's law states that the total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps, regardless of the pathway taken. To measure the enthalpy of a desired reaction, one can manipulate known reactions with known enthalpy changes to create a series of steps that lead to the desired reaction. By adding or subtracting these enthalpy changes accordingly, the overall enthalpy change for the desired reaction can be calculated. This method is particularly useful when the desired reaction cannot be measured directly.
Why does Hess's law allow you to determine the enthalpy change of a reaction?
Hess's law states that the total enthalpy change for a chemical reaction is the sum of the enthalpy changes for each individual step of the reaction, regardless of the pathway taken. This allows us to determine the enthalpy change of a reaction by adding the enthalpy changes of multiple known reactions that, when combined, yield the desired overall reaction. By using this principle, we can calculate enthalpy changes even when the reaction cannot be measured directly. Thus, Hess's law provides a systematic way to obtain enthalpy values from existing data.
Why you measure enthalpy in H instead of H?
The total enthalpy of a system is called "H." That stands for "total enthalpy." It is not a measure of enthalpy. Enthalpy is measured in the SI or metric system in joules (abbreviated as J) or in customary units such as British Thermal Unit (BTU) or calories (cal).
Why can't the enthalpy change of combustion of CO2 be measured?
The enthalpy change of combustion of CO2 cannot be measured directly because CO2 is already in its most stable form. In combustion reactions, compounds react with oxygen to form more stable products, releasing heat. Since CO2 is already at the end of the combustion process and cannot be further reacted to release more heat, its enthalpy change of combustion cannot be measured directly.
What is hess's law used to measure enthalpy of a desired reaction?
Hess's Law states that the total enthalpy change for a chemical reaction is the same, regardless of the pathway taken, provided the initial and final states are the same. This principle allows for the calculation of the enthalpy change of a desired reaction by using the enthalpy changes of multiple intermediate reactions that add up to the overall reaction. By summing these known enthalpy changes, one can derive the enthalpy of the target reaction, even if it cannot be measured directly. This makes Hess's Law a valuable tool in thermochemistry for determining reaction enthalpies.
Define hardness as it is measured on a rockwell or brinell testing instrument?
hardness as it is measured on a rockwell or brinell testing instrument
Which reaction shows that the enthalpy of formation of C2H4 is Hf 52.5 kJmol?
The enthalpy of formation (ΔH_f) of C2H4 can be demonstrated through the reaction of its constituent elements in their standard states. This can be represented by the equation: 2C (s) + 2H2 (g) → C2H4 (g). If the enthalpy change for this reaction is measured to be +52.5 kJ/mol, it indicates that the formation of ethylene (C2H4) from its elements requires 52.5 kJ of energy, thus confirming its enthalpy of formation.
What is the relationship between enthalpy of atomisation of hydrogen and the bond dissociation enthalpy of the H-H bond?
the enthalpy of atomisation of hydrogen is equal and (in principle) identical to the bond dissociation enthalpy of the H-H bond. However, IF the first is measured by calorimetry and the second by spectrometry there might be a systematic difference.
