Similarly, by dividing a mass (in grams) by the molar mass (in g/mol), you get a molar amount.įor example, StudySmarter-ium has one of each element, so the molar mass of the compound is just the sum of the atomic masses of all the components, which is 1181.37 g/mol. Multiplying a molar amount (number of atoms in a compound) by their molar mass gives you weight (in grams). The molar mass of a compound is calculated by adding up the atomic mass of each element in the compound. Molar mass is a crucial concept in chemistry because it allows us to calculate how many grams of atoms we need instead of counting up atoms one by one. Let's add all of them together to get the molar mass of the compound/molecule! Do it yourself for water and amphetamine, you will need it in the next step! 3. So in this case: 32.07 g/mol for Sulfur, 204.38 g/mol for Thallium, and so on until we get to 226.03 g/mol for Radium. The numbers below the names of the elements are the average atomic masses, but in this case, we only have one of each, so there are no numbers in the compound formula. Let's do this one for the ST(i)UDySmArTeR(a) molecule (hint: look at the figure above). Get the atomic masses from the periodic table. Similarly, amphetamine, an organic compound, has the chemical formula C9H13N meaning it has 9 C, 13 H and 1 N atom. Water has the chemical formula H2O which means it has 2 H atoms and 1 O atom. Count the number of atoms of each element which make up the compound/molecule. If you repeat these steps ,you will always be able to calculate the correct molar mass, no matter how complicated your compound is. I will first give you a list of steps (kind of like an algorithm for a computer) to get to the final molar mass. ‍ How do you calculate the molar mass of a compound?Ĭalculating the molar mass of a compound is pretty straightforward, but I won't write it in the form of an equation (yet) because that makes it unnecessarily complicated and scary for most students. The molar mass of a compound can be found on the periodic table, usually under the name of the element. For example, the molar mass of iron (II) chloride (FeCl2) is calculated by multiplying the atomic mass of iron (56 g/mol) by the number of atoms of iron (1), and then multiplying the atomic mass of chlorine (35.5 g/mol) by the number of atoms of chlorine (2). It is calculated by multiplying the atomic mass of each element in the compound by the number of atoms of that element in the compound, and then adding the results together. Molar mass is the ratio of the mass of a molecule compared to the unified atomic mass unit. Recap: The periodic table with molar masses 'Moles and Molar Mass' and 'Avogadro's Number and the Mole' are both great places to start. We have articles on our site that can help you understand the basics before we get into calculating. For now, you can use the terms interchangeably. But, if we ever do chemistry on other planets or in space, we will use atomic mass. When we do chemistry on Earth, we use atomic weight. Atomic weight is what you would measure for the atomic mass near (or on the surface of) a heavy object. The units for both measures are atomic mass units.Ītomic mass is defined as the rest mass of an atom, usually expressed in atomic units. This helps you figure out the molecular mass by adding up the atomic masses.

So, you use something called atomic mass to calculate how much they weigh. You face a similar problem every day - you need to know how many atoms you need, but counting them out one by one is impossible. In this case, it would be 10 kilograms of sand per batch of cement.

Then you can calculate the total weight of sand you need. That means each grain is 1/10th of a milligram. Let's say you find out that each grain of sand weighs 10 milligrams. To figure out how much sand you need, you can measure the weight of an average grain of sand by weighing 100 of them on a scale. Have you ever been given a task with a really specific requirement? Like, for instance, at a construction site, where the engineer says you need to use 100 million grains of sand for every batch of cement mixed? You might think you need to sit there and count out every grain of sand, but there's a better way to do things.

Periodic table with new molar mass