12% NaCl is the answer I came to... Have a GREAT day!!! :)
We need to find the Ka value of HF. First, set up the balanced chemical equation:
HF ===> H+ + F-
The formula for the Ka value of an acid is
Ka = [concentration of products] / [concentration of reactants]
Ka = [H+] [F-} / [HF]
So if we are given the concentration of the products and reactants, we will be able to solve for the Ka value of HF.
8) The gravitational force is a force of attraction between two objects. It can be expressed mathematically as:
F = G m₁*m₂/d² ------(1)
m₁ and m₂ are the masses of two interacting systems
d = distance between them
G = gravitational constant
Thus according to equation(1), the gravitational force is directly proportional to the mass of the objects. Greater the masses, stronger will be the force of attraction.
In this case, the distance (d) and the one of the masses i.e. mass of earth would be the same for both situations. However, since an elephant would weigh more than a human, the gravitational force will be stronger between an elephant and earth.
9) Since the masses of spheres is the same, the gravitational force between the red and blue spheres would be the same as well, provided the distance d remains constant.
Carbon dioxide, or

, is a pure covalent bond.
pure - it's non-polar, because it's a linear & symmetrical bond.
covalent - covalence is when 2 electrons are shared by a pair of atoms. in the case of carbon dioxide, it's three atoms with an oxygen atom on the right, an oxygen atom on the left, and a carbon atom smack in the middle. 2 of carbon's extra electrons are shared with the right oxygen, and 2 other extra atoms are shared with with left oxygen.