Answer:
A, C and D are correct.
Explanation:
Hello.
In this case, since the relationship between the vapor pressure of a solution is directly proportional to the mole fraction of the solvent and the vapor pressure of the pure solvent as stated by the Raoult's law:
Since the solute is not volatile, the mole fraction of the solute is not taken into account for vapor pressure of the solution, therefore A is correct whereas B is incorrect.
Moreover, since the higher the vapor pressure, the weaker the intermolecular forces due to the fact that less more molecules are like to change from liquid to vapor and therefore more energy is required for such change, we can evidence that both C and D are correct.
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Answer:
This experiment is uncontrolled because two different masses of substance A are used.
Explanation:
A controlled experiment is a structured experiment aimed at testing a particular observation or observations. The setup of a controlled experiment helps to determine the reason why a particular observation occurs and what must have led to it.
In the experiment highlighted above, different masses of a substance were used, they were heated to different temperatures. The set up does not show any correlation between the masses of substances heated and the temperatures. It is even difficult to try to predict the hypothesis for this kind of experimental set up. All the variables in play can best be assumed to be independent of one another.
Answer:
Maintenance of homeostasis usually involves negative feedback loops. These loops act to oppose the stimulus, or cue, that triggers them.
Answer :
The correct answer for primary component of phosphate buffer at pH = 7.4 is H₂PO₄⁻ and HPO₄²⁻ .
<u>Buffer solution :</u>
It is a solution of mixture of weak acid and its conjugate base OR weak base and its conjugate acid . It resist any change in solution when small amount of strong acid or base is added .
<u>Capacity of a good buffer : </u>
A good buffer is identified when pH = pKa .
From Hasselbalch - Henderson equation which is as follows :
![pH = pka + log \frac{[A^-]}{[HA]}](https://tex.z-dn.net/?f=pH%20%3D%20pka%20%2B%20log%20%5Cfrac%7B%5BA%5E-%5D%7D%7B%5BHA%5D%7D)
If [A⁻] = [HA] ,
pH = pka + log 1
pH = pKa
This determines that if concentration of weak acid and its conjugate base are changed in small quantity , the capacity of buffer to maintain a constant pH is greatest at pka . If the amount of [A⁻] or [HA] is changed in large amount , the log value deviates more than +/- 1M and hence pH .
Hence Buffer has best capacity at pH = pka .
<u>Phosphate Buffer : </u>
Phosphate may have three types of acid-base pairs at different pka ( shown in image ).
Since the question is asking the pH = 7.4
At pH = 7.4 , the best phosphate buffer will have pka near to 7.4 .
If image is checked the acid - base pair " H₂PO₄⁻ and HPO₄²⁻ has pka 7.2 which is near to pH = 7.4 .
Hence we can say , the primary chemical component of phosphate buffer at pH = 7.4 is H₂PO₄⁻ and HPO₄²⁻ .
Half-life is defined as the quantity to reduce to half of its initial value.
Explanation:
The term half-life is generally used in nuclear physics which describes how long a stable atom can survive a radioactive decay or how quickly an unstable stable atom can undergo radioactive decay. Half-life is a constant and does not have any units.
<u>The formula to calculate half-life:
</u>
N(t) = 
Here N(t) is the quantity which is “not decayed”.
is the “initial quantity” of the substance.
λ is the “decay constant”
