Answer:
This is a physical change because it's not permanent and no chemical reaction occurs. Mixtures - Mixing together materials where one is not soluble in the other is a physical change. Note the properties of a mixture may be different from its components.
Explanation:
The difference between a physical reaction and a chemical reaction is composition. In a chemical reaction, there is a change in the composition of the substances in question; in a physical change there is a difference in the appearance, smell, or simple display of a sample of matter without a change in composition.
In a physical change, the molecules are rearranged while their actual composition remains same. In a chemical change, the molecular composition of a substance completely changes and a new substance is formed. Some example of physical change are freezing of water, melting of wax, boiling of water....
Hg2O -> O2 + Hg
2Hg2O -> O2 + 2Hg
20g-> ?g + 18.6g
(1 molHg2O ) (1 mol O2) (32g O2)
20g 2Hg2O x ------------------- x ------------------- x -------------- = 0.77g O2
(834.36Hg2O) (1 mol Hg2O) (1 mol O2)
I think this is done to allow even distribution of temperature in all the regions of the calorimeter. That is to make sure that there are no hot or cold spots and also ensure that the measured temperature is the actual average temperature when the readings are taken by a thermometer.
Answer: ratio is 10⁻⁵
Explanation:
From Acid-dissociation equilibrium constant, HA is given thus,
HA + H₂O ⇄ H₃O⁺ + A⁻
equilibrium constant, Ka = [H₃O⁺] [A⁻] / [HA]
[H₃O⁺] = Ka [HA] / [A⁻]
from this we have that
pH = -log[H₃O⁺]
and pKa = -logKa
Applying Henderson-Hassel bach equation;
pH = pKa + log [A⁻]/[HA] ...........(1)
A⁻ rep the salt and HA rep the acid
at a given pH of 7, the pKa value of carboxylic acid COOH is 3
∴ from equation (1).
7 = 3 + log(COO⁻/COOH)
log(COO⁻/COOH) = 4
thus (COO⁻/COOH) = 10⁻⁴ ...................(2)
The ratio of alanine COOH to COO- at pH 7 is (COO⁻/COOH) = 10⁻⁴
(ii) Also considering the ratio of alanine NH2 to NH3+ at pH 7 we have;
given Pka value is 8,
therefore pH = pKa + log [salt]/[base]
7 = 8 + log (NH₂/NH₃)
(NH₂/NH₃) = 10⁻¹
thus the ratio of the concentration of the neutral amino acid species to the zwitterionic species at pH 7 is;
10⁻⁴ ˣ 10⁻¹ = 10⁻⁵
cheers i hope this helps