The percent by mass sugar of a solution : 11.07%
<h3>Further explanation</h3>
Given
mass of sugar = 12.45 g
mass of water = 100 g
Required
The percent by mass
Solution
Mass of solution :
Percent mass of sugar :
First we have to find Ka1 and Ka2
pKa1 = - log Ka1 so Ka1 = 0.059
pKa2 = - log Ka2 so Ka2 = 6.46 x 10⁻⁵
Looking at the values of equilibrium constants we can see that the first one is really big compared to second one. so, the pH will be affected mainly by the first ionization of the acid.
Oxalic acid is H₂C₂O₄
H₂C₂O₄ ⇄ H⁺ + HC₂O₄⁻
0.0356 M 0 0
0.0356 - x x x
Ka1 =
= x² / 0.0356 - x
x = 0.025 M
pH = - log [H⁺] = - log (0.025) = 1.6
This question includes four answer choices:
A. definite volume, highest molecular motion, highest kinetic energy
B. indefinite volume, least molecular motion, highest kinetic energy
C. definite volume, least molecular motion, lowest kinetic energy
D. definite volume, no molecular motion, lowest kinetic energy
Solids do not have the highest molecular motion (on the contrary they have the least molecular motion), so you can discard option A. Solids have a definite volume and the highest kinetic energy (given that they have the least molecular motion), so you discard option C. Molecules always have a vibrational motion, so you discard option D. Option C, have only characteristics that correctly describes a solid: definite volume, least molecular motion, lowest kinetic energy. Therefore, the answer is the option C.
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