You might be able to roughly estimate mass in a visual manner, but it could be easy to dismiss the fact that a mole or even a gram represents a significantly large number of molecules. Avogadro's number, 6.022×1023, describes how many molecules, atoms, or particles are in one mole of a substance. We use moles to describe and compare amounts because the values correspond to the macroscopic scale in which we operate. Let us consider a reaction that takes place between relatively low masses. In Sample 2 from the simulation, carbon monoxide gas (CO) can react with hydrogen gas (H2) to form methanol (CH3OH), which is a liquid at room temperature. If you had a sealed reaction vessel that was vacuum pumped, and measured its change in mass as you introduced each reactant gas to the vessel, you could determine the amount of each gas that entered the vessel by those measured changes in mass.

If 1.50 μg of CO and 6.80 μg of H2 were added to a reaction vessel, how many total gas particles would remain in the reaction vessel after the reaction went to completion? Assume no gas particles dissolve into the methanol.

Express the number of particles to three significant digits.