Indicate whether each statement about the nucleus of an atom is true or false.

1. the nucleus of an atom is neutral. the nucleus of an atom contains only neutrons.
2. the number of nucleons present in the nucleus is equal to the number of electrons present outside the nucleus.
3. the nucleus accounts for almost all the volume of an atom. the nucleus accounts for almost all the mass of an atom.
4. the nucleus can be positively or negatively charged depending on the identity of the atom.

1) false

2)false

3) true

4)false

Explanation:

The nucleus contains neutrons and protons; the nucleus is positively charged because of the protons present. The neutrons have no charge. The number of protons in a neutral atom equals the number of orbital electrons. The neutrons have almost the same mass as the protons while the electrons have a negligible mass. Hence, protons and neutrons account for most of the mass of the atom. The mass of the atom is concentrated in the nucleus.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%