Answer:
The correct answer is 190.5 mL of 1.00 M KH₂PO₄
Explanation:
A phosphate buffer is composed by phosphate acid (KH₂PO₄) and its conjugated base (K₂HPO₄). To obtain the relation between the concentrations of base and acid to add, we use Henderson-Hasselbach equation:
pH= pKa + log 
We have: pH= 6.97 and pKa= 7.21. So, we replace the values in the equation:
6.97= 7.21 + log
6.97-7.21= log
-0.24= log
=
0.575 =
=
It means that you have to mix a volume 0.575 times of conjugated base and 1 volume of acid. If we assume a total buffer concentration of 1 M, we have:
base + acid = 1
base= 1 - acid
We replace in the previous equation:
0.575= 
0.575 acid= 1 - acid
0.575 acid + 1 acid= 1
1.575 acid = 1
acid= 1/1,575
acid= 0.635
base= 1 - acid = 1 - 0.635 = 0.365
For a total volume of 300 ml, the volumes of both acid and base will be:
300 ml x 0.635 M = 190.5 ml of acid (KH₂PO₄)
300 ml x 0.365 M= 109.5 ml of base (K₂HPO₄)
We can corroborate our calculations as follows:
190.5 ml + 109.5 ml = 300 ml
109.5 ml / 190.5 ml = 0.575
13.29 multipled by 25
the answer is 332.25 grams
Because of the attraction forces known as hydrogen bonding, water is referred to as a polar solvent. An attraction between molecules known as a hydrogen bond occurs when partially positive hydrogen atoms are drawn to partially negative F, O, or N atoms.
<h3>What is a hydrogen bond?</h3>
A hydrogen bond (or H-bond) is a strong electrostatic attraction between an electronegative atom holding a lone pair of electrons, known as the hydrogen bond acceptor, and a hydrogen (H) atom that is covalently attached to a more electronegative "donor" atom or group.
<h3>How can hydrogen atoms join together?</h3>
When a hydrogen atom bonds with an electronegative atom, powerful intermolecular forces called hydrogen bonds are produced. The hydrogen bond acceptor's electronegativity will rise, resulting in a stronger hydrogen bond.
To know more about Hydrogen Bond visit:
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Applied force
Gravitational force
And Normal force
To find the empirical formula you would first need to find the moles of each element:
58.8g/ 12.0g = 4.9 mol C
9.9g/ 1.0g = 9.9 mol H
31.4g/ 16.0g = 1.96 O
Then you divide by the smallest number of moles of each:
4.9/1.96 = 2.5
9.9/1.96 = 6
1.96/1.96 = 1
Since there is 2.5, you find the least number that makes each moles a whole number which is 2.
So the empirical formula is C5H12O2.
