Sometimes the amounts of gases need to be calculated based on chemical reactions. These calculations combine the ideal gas laws and the same principles we learn in stoichiometric calculations. The only difference for most problems is going to be that the … Read more
Hess’s law allows measuring the enthalpy change (ΔH) for a reaction without making calorimetric measurements. To do this, we need the enthalpies of some other reactions. For example, Using the given data for reactions (1) and (2), calculate the ΔH for … Read more
Standard enthalpy of formation (or heat of formation), ΔHof , is the enthalpy change when 1 mol of the substance is formed from its constituent elements in their standard states. For example, the formation of 1 mol ammonia from H2 … Read more
The enthalpy change for a chemical reaction (ΔHrxn), also known as the enthalpy of reaction or heat of reaction is often given next to the chemical equation. These are called thermochemical equations. For example, the enthalpy change for the combustion … Read more
Different objects require a different amount of heat to increase their temperature. For example, if you heat a beaker with 100 g of water and a 100-g iron plate, the latter will reach a high temperature a lot faster than … Read more
The first law of thermodynamics is the law of energy conservation, which states that energy can be converted from one form to another, but cannot be created or destroyed. One implication of this law is that the total energy of … Read more
In the previous post, we talked about partial pressures and the Dalton law. Today, we will see how the mole fraction and partial pressures of a gas are related. Remember, mole fraction (Χ) is the ratio of the moles of … Read more
To understand the partial pressures, let’s suppose a certain amount of gas “A” is added to a tank and exerts 5 atm pressure, and in another tank with gas “B” the pressure is 3 atm: Now, it turns … Read more
The mixing of different gas molecules by random molecular motion and frequent collisions is called diffusion. An example of this can be the raid odor spread of perfume when the stopper is removed. Effusion is a similar process in which … Read more
Density and molar mass are calculated by modifying the ideal gas law equation. What we do is first replace the moles (n) in PV = nRT with mass over the molar mass: … Read more
