Welcome to this deck on Quantitative Chemistry. This topic is all about the numbers in chemistry – how we measure amounts of substances and use them to understand chemical reactions. We'll cover how to calculate the relative formula mass of a compound, explore the law of conservation of mass, and see why we need to balance equations. We'll also introduce a crucial chemical unit called the mole, and use it to calculate masses and concentrations. Finally, we'll look at what happens when one reactant runs out before another.

Before we can work with compounds, we need to understand the mass of individual atoms. The mass of an atom is given by its relative atomic mass, often shown with the symbol A r. You can find the relative atomic mass for any element by looking at the mass number on the periodic table. For example, carbon's mass number is 12, so its relative atomic mass is 12. This number tells us how heavy an atom of that element is compared to other atoms.

Now, let's look at compounds. The relative formula mass of a compound, with the symbol M r, is simply the sum of the relative atomic masses of all the atoms in its chemical formula. For example, carbon dioxide has the formula C O two. To find its M r, we find the A r of carbon, which is 12, and add it to the A r of two oxygen atoms. Oxygen's A r is 16, so two of them is 32. Therefore, the M r of carbon dioxide is 12 plus 32, which equals 44.