How many h20 molecules are in 18 grams of water

For H 2 O we have:. It takes 18 grams of H 2 O to obtain 1 mole, or 6. Think about that before we answer the question. We have To find the exact number, divide the available mass Watch how the units work out. The grams cancel and moles moves to the top, leaving moles of water. Multiply 1. That's slightly above Avogadro's number, which is what we expected. Keeping the units in the calculations is annoying, I know, but it helps guide the operations and if you wind up with the unit desired, there is a good chance you've done the problem correctly.

There are 6. This is Avogadro's number. Get a free answer to a quick problem. Most questions answered within 4 hours. Choose an expert and meet online. No packages or subscriptions, pay only for the time you need. Chemistry Moles. Add comment. As an example, let's say we have a very tiny drop of water, say 1 microliter, which would have a mass of 0. The chemical formula for water is H 2 O which means that every molecule of water has 2 atoms of hydrogen H and one atom of oxygen O.

Here comes the key part. From the Periodic Table of Elements , one sees that one mole of hydrogen atoms weighs 1 gram while one mole of oxygen atoms weighs 16 grams. What is this mole thing? A mole is a convenient counting unit whenever one is dealing with numbers of atoms or molecules.

It is equal to Avogadro's number NA , namely 6. Since we only have 0.