How do I calculate moles from the given litres and mass of the substance (in grams)?
To calculate the number of moles from the given liters and mass of a substance in grams, you need to follow a series of steps:
Step 1: Convert the given mass from grams to moles using the molar mass of the substance. The molar mass of a substance is the mass of one mole of that substance and is expressed in grams per mole. You can find the molar mass of an element or a compound by adding up the atomic masses of its constituent elements.
Step 2: Convert the given volume from liters to moles using the molar volume of the substance. The molar volume is the volume occupied by one mole of a substance at a specific temperature and pressure. For gases at standard temperature and pressure (STP), the molar volume is approximately 22.414 liters per mole.
Here's an example to illustrate the calculation:
Let's say you have 4.5 liters of a gas with a mass of 36 grams. You want to calculate the number of moles.
Step 1: Calculate moles from mass
First, determine the molar mass of the gas. Let's assume it is 28 grams/mol.
To calculate moles from mass, you use the formula:
moles = mass / molar mass
Plugging in the values:
moles = 36 grams / 28 grams/mol
moles = 1.286 moles
Step 2: Calculate moles from volume
Assuming the gas is at STP, the molar volume is approximately 22.414 liters/mol.
To calculate moles from volume, you use the formula:
moles = volume / molar volume
Plugging in the values:
moles = 4.5 liters / 22.414 liters/mol
moles = 0.201 moles
Therefore, the final answer is that you have approximately 0.201 moles of the gas.
By following these steps, you can calculate the number of moles from the given liters and mass of a substance.