The law of conservation of mass applies to both cases, the following will explain how:
1. When 50 g of sugar undergoes a physical change, say for example dissolving or melting, the amount of sugar in the solution or melted form will also be 50 grams. This shows that the mass before and after the change was the same, in accordance to the law of conservation of mass.
2. When the magnesium strip is burned, this is a chemical reaction. The problem is that we only measure the mass of one of the substances involved in the reaction, the magnesium strip, which makes it seem like the mass has increased. Actually, during burning, the magnesium combines with oxygen in the air. This oxygen was present before the reaction, we just did not measure it. And after the reaction it is present in the form of product. Therefore, mass is still conserved.
The ph of a saturated solution of Ca(OH)2 is 12.35
CALCULATION:
For the reaction
Ca(OH)2 → Ca2+ + 2OH-
we will use the Ksp expression to solve for the concentration [OH-] and then use the acid base concepts to get the pH:
Ksp = [Ca2+][OH-]^2
The listed Ksp value is 5.5 x 10^-6. Substituting this to the Ksp expression, we have
Ksp = 5.5 x 10^-6 = (s) (2s)^2 = 4s^3
s3 = 5.5x10^-6 / 4
Taking the cube root, we now have
s = cube root of (5.5x10^-6 / 4)s
= 0.01112
We know that the value of [OH-] is actually equal to 2s:
[OH-] = 2s = 2 * 0.01112 = 0.02224 M
We can now calculate for pOH:
pOH = - log [OH-]
= -log(0.02224)
= 1.65
Therefore, the pH is
pH = 14 - pOH
= 14 - 1.65
= 12.35
Answer:
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Explanation:
