A party balloon contains 5.50 x 10 ^22 atoms of helium gas. What is the mass, in grams of the helium?

a) 0.365 g He
b) 9.14 x 10^-2 g He
c) 0.365 mol He
d) 9.14 x 10 -2 mol He

Explanation:

1. Convert Atoms to Moles

We must use Avogadro's Number: 6.022*10²³. This is the number of particles (atoms, molecules, ions, etc.) in 1 mole of a substance. In this case, the particles are atoms of helium. We can create a ratio.

Multiply by the given number of helium atoms.

Flip the fraction so the atoms of helium cancel.

2. Convert Moles to Grams

We must use the molar mass, which is found on the Periodic Table.

Use this as a ratio.

Multiply by the number of moles we calculated. The moles will then cancel.

3. Round

The original measurement has 3 significant figures (5, 5, and 0). Our answer must have the same. For the number we calculated, it is thousandth place. The 3 in the ten thousandth place tells us to leave the 5.

The mass is 0.365 grams of helium so choice A is correct.

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

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