How many molecules of H2O are contained in 78.34 grams? 6.342 X 1019 molecules

2.618 X 1024 molecules

5.634 X 1025 molecules

9.984 X 1022 molecules

1.198 X 1026 molecules

4.716x10^25

Explanation:

1 molecule of water is equivalent to 6.02x10^23

hence 78.34 is equivalent to 78.34x6.02x10^23

and the answer is 4.716x10^25

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.