8. A. Density is independent of size (an intensive property).
9. B. The highest density is 1786 g/20cm^3, or 89.3 g/cm^3. The least is 512 g/20cm^3, or 25.6 g/cm^3. Therefore, the difference is 89.3 - 25.6, or 63.7 g/cm^3.
10. C. A bottle filled with air weighs less than one filled with marshmallows, because air is less dense than marshmallows.
11. D. The number represents the number of protons in the nucleus of the atom, as well as the atomic number of the element.
12. C. The number represents the atomic mass of the element, which is determined based on the relative abundance of each form of the element.
Answer:
at first i would like to tell which class
Explanation:
125000 is the answwr
A solid that forms and separates from a liquid mixture is a chemical change.
Answer:
(a) 
(b) 
(c) 
(d) 
(e) 
Explanation:
To calculate de pH of an acid solution the formula is:
![pH = -Log ([H^{+}]) = 1](https://tex.z-dn.net/?f=pH%20%3D%20-Log%20%28%5BH%5E%7B%2B%7D%5D%29%20%3D%201)
were [H^{+}] is the concentration of protons of the solution. Therefore it is necessary to know the concentration of the protons for every solution in order to solve the problem.
(a) and (c) are strong acids so they dissociate completely in aqueous solution. Thus, the concentration of the acid is the same as the protons.
(b) and (e) are strong bases so they dissociate completely in aqueous solution too. Thus, the concentration of the base is the same as the oxydriles. But in this case it is necessary to consider the water autoionization to calculate the protons concentration:
![K_{w} =[H^{+} ][OH^{-}]=10^{-14}](https://tex.z-dn.net/?f=K_%7Bw%7D%20%3D%5BH%5E%7B%2B%7D%20%5D%5BOH%5E%7B-%7D%5D%3D10%5E%7B-14%7D)
clearing the ![[H^{+} ]](https://tex.z-dn.net/?f=%5BH%5E%7B%2B%7D%20%5D)
![[H^{+} ]=\frac{10^{-14}}{[OH^{-}]}](https://tex.z-dn.net/?f=%5BH%5E%7B%2B%7D%20%5D%3D%5Cfrac%7B10%5E%7B-14%7D%7D%7B%5BOH%5E%7B-%7D%5D%7D)
(d) is a weak base so it is necessary to solve the equilibrium first, knowing 
The reaction is
→
so the equilibrium is

clearing the <em>x</em>

![x=[H^{+}]=4.93x10^{-10}](https://tex.z-dn.net/?f=x%3D%5BH%5E%7B%2B%7D%5D%3D4.93x10%5E%7B-10%7D)