Answer:
I am beginner so,
The appearance of the clock will not change, but it's sound will become fainter.
Your answer is 20.7298014
For one mole of hydrogen, H, the atomic mass is 1 g per mole. Hydrogen contains 1 proton and zero neuton. A neutral atom of hydrigen also contains 1 electron.
For the first one, compound might mean more than one thing or i team. But mixture is a very specific definition for chemistry. And for the second one, it would be wrong because “pure” means only that substance, where as it would only be “orange juice”, or something else. But pure refers to only a clean not contaminated substance.