state formula mass with example
Answers
Substances take up space and have mass. Molecules, which make up substances, often need to be measured in experiments, and it is important that these measurements are accurate. But, how can we measure something so small in an accurate way? How do we normally measure molecules? In the science laboratory, we use a tool called an analytical balance to measure in grams.
Through careful calculation, scientists can determine the number of moles a specific reaction will need. A mole is a unit of measure that helps us compare particles of any given substance and its mass. If we already know the number of moles needed, we can use the concept of molar mass to calculate how many grams of the substance are required. The molar mass, also known as molecular weight, is the sum of the total mass in grams of all the atoms that make up a mole of a particular molecule. The unit used to measure is grams per mole.
Step 1: Find the atomic masses of individual elements in the periodic table
The first thing we need is to find the individual atomic masses for each element. If you look at the entries for sodium and chlorine in the table, we will pay attention to the numbers that appear in the top left (see video). These represent the atomic mass. The element sodium has an atomic mass of 22.98976 g/mol. The element chlorine has an atomic mass of 35.453 g/mol.
Step 2: Count how many atoms there are for each element
For the compound sodium chloride, since there are no subscripts (small numbers at the bottom of each element's symbol), that means there is only one sodium and only one chlorine atom for this compound.
Step 3: Find the molar mass
The formula mass of a molecule is the sum of atomic weights of the atoms in the compound. It is also known as formula weight and is given in 'amu'.