How many molecules of hydrogen chloride gas are in 1.5 x 10-3 hectoliters of the substance at STP?

Question

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Answer 1

What is a hectoliter? It is 100 liters (10² liters)

At STP (standard temperature and pressure) 1 mole of any ideal gas occupies 22.4 liters. So, we need to find the number of moles present in 1.5x10-3 hectoliters, and then convert that to molecules using Avogadro's number.

moles of HCl gas = 1.5x10^-3 hectoliters x 10² liters / hectoliter x 1 mol / 22.4 L = 0.006696 moles HCl gas

molecules of HCl gas = 0.006696 moles x 6.02x10²³ molecules / mol = 4.0x10²¹ molecules of HCl gas