Most scientific questions are developed from Observations.
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.
where are equations dear????
Na₃PO₄ -----> 3Na(+) + PO₄(3-)
y-y.......................3y...........y
3y = 1.2
y = 0,4M
Na₃PO₄ -----> 3Na(+) + PO₄(3-)
0,4-0,4..............1,2..........0,4
0.........................1,2..........0,4
C = n/V
n = C×V
n = 0,4×0,65L
n = 0,26 mol Na₃PO₄
mNa₃PO₄: (23×3)+31+(16×4) = 164 g/mol
164g ----- 1 mol
Xg -------- 0,26 mol
X = 164×0,26
X = 42,64g Na₂SO₄