Explanation:
According to the Henderson-Hasselbalch equation, the relation between pH and
is as follows.
pH = 
where, pH = 7.4 and
= 7.21
As here, we can use the
nearest to the desired pH.
So, 7.4 = 7.21 + 
0.19 = 
= 1.55
1 mM phosphate buffer means
+
= 1 mM
Therefore, the two equations will be as follows.
= 1.55 ............. (1)
+
= 1 mM ........... (2)
Now, putting the value of
from equation (1) into equation (2) as follows.
1.55
= 1 mM
2.55
= 1 mM
= 0.392 mM
Putting the value of
in equation (1) we get the following.
0.392 mM +
= 1 mM
= (1 - 0.392) mM
= 0.608 mM
Thus, we can conclude that concentration of the acid must be 0.608 mM.
I think it was sue to she has all the details to seem like it was her
Answer : The correct option is, (d) inversely proportional to volume and directly proportional to the kelvin temperature
Explanation :
Boyle's Law : It is defined as the pressure of the gas is inversely proportional to the volume of the gas at constant temperature and number of moles.

Charles' Law : It is defined as the volume of the gas is directly proportional to the temperature of the gas at constant pressure and number of moles.

Gay-Lussac's Law : It is defined as the pressure of the gas is directly proportional to the temperature of the gas at constant volume and number of moles.

Combined gas law : It is the combination of Boyle's law, Charles's law and Gay-Lussac's law.
The combined gas equation is,

or,

From the above information we conclude that the pressure exerted by a gas is inversely proportional to volume and directly proportional to the kelvin temperature.
Hence, the correct option is, (d)
I'm assuming that you meant 55 g/cm^
3. Density=

. This is the definition of density. If you rearrange this equation by multiplying each side of the equation by the volume, you get: (Density)(Volume)=Mass. Divide each side by the density to get: Volume=Mass/Density. Now just plug everything in:
V=220 (grams)/55 (grams/cm^3)=<u>4 cm^3</u>