Answer:
C) HF, because it has the strongest intermolecular force
Explanation:
The electronegativity difference ΔEN between H and F is so high that HF has especially high dipole-dipole forces, which we call hydrogen bonds. They are the strongest intermolecular forces, and they are responsible for the high boiling point of HF.
A) is wrong. HI has a higher mass and more electrons than HBr.
B) is wrong. There is no hydrogen bonding in HCl.
D) is wrong. There are no ion-dipole forces in HI.
Atomic number of gold, 
= 79 means there are 79 electrons in per atom of gold.
Atomic mass of gold = 196.967 gm
0.990 oz of gold is given.
Now, converting 
So, 
Now, for determining the number of moles, the formula for number of moles is:
Substituting the values:
1 mole of 
So, for 0.1425 mole of 
Since 1 atom of gold has 79 electrons so,
Number of electrons = 
So, number of electrons in 0.990 oz of pure gold coin is 
.
I think it is 1.1g/mL if i got my sig figs down
Answer:
Question 2: Because the elements could be unstable, forming elemental compounds.
Question 1: Water is made up of Hydrogen and oxygen, which is namely called H2^o What makes it a pure substance is the little mass and molecules it's made up of.
An isotope is an atom with a different number of neutrons than another atom of the same element. Since atoms of the same element all have the same number of protons, choice B(6pro &6neu vs. 6pro&7neu) is an example of isotopes
