# How many times are 3 g of hydrogen more molecules than 9 g of water? The molar mass of hydrogen

How many times are 3 g of hydrogen more molecules than 9 g of water? The molar mass of hydrogen is 2 kg / kmol, water is 18 kg / kmol.

Given:

m1 = 3 g is the mass of hydrogen;

m2 = 9 g is the mass of water;

M1 = 2 kg / kmol = 2 * 1000/1000 g / mol = 2 g / mol;

M2 = 18 kg / kmol = 18 * 1000/1000 g / mol = 18 g / mol;

N1 / N2 -?

Decision:

formula for the number of hydrogen molecules: N1 = m1 * Na / M1, where Na is Avogadro’s constant;

formula for the number of water molecules: N2 = m2 * Na / M2;

N1 / N2 = m1 * Na * M2 / m2 * Na * M1, Na in the numerator and denominator are canceled;

N1 / N2 = m1 * M2 / m2 * M1;

N1 / N2 = 3 * 18/9 * 2 = 54/18 = 3 times.

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