If you divide 8.1 by 1.8 that leads to 4.5
The stock solution contains 10.5 moles of HCl per litre. A 5.5 litre solution of 2.5M HCl contains 5.5x2.5 = 13.75moles of HCl. Since every litre of stock solution provides 10.5M HCl, the amount of stock solution needed is 13.75/10.5 = 1.309L. Therefore you would dilute 1.309L of stock solution to 5.5L
Polar Covalent.
This is because both Calcium (Ca) and Carbon (C) are non metals, thus eliminating the ionic option.
It is polar covalent rather than nonpolar covalent due to the fact that the electrons in a polar covalent bond are shared unequally while those in a nonpolar bond are shared equally.
This can be determined by looking at the amount of valence electrons; if the electrons cancel each other out, it is shared equally. If not, it is shared unequally.
Hope this helps!
<span>Because protons are positively charged and neutrons have no charge then it is safe to say that such an atomic model would have the positive charge concentrated in the center of an atom (option d).</span>