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
Answer:
If the electronegativity of two atoms is basically the same, a nonpolar covalent bond will form, and if the electronegativity is slightly different, a polar covalent bond will form.
Explanation:
that's your answer very easy.
Answer:
WCl₂, WCl₄, WCl₅, WCl₆
Explanation:
Molar Mass of Tungsten = 184 g/mol
Mass of Chlorine = 35.5 g/mol
In the first compound;
Percentage of tungsten = 72.17 %
Upon solving;
72.17 % = 184
100 % = Total mass
Total mass of compound = 254.95g
Mass of chlorine = 254.95 - 184 = 70.95 (Dividing by 35.35; This is approximately 2 Chlorine atoms.
The Formular is WCl₂
In the second compound;
Percentage of tungsten = 56.45 %
Upon solving;
56.45 % = 184
100 % = Total mass
Total mass of compound = 325.95 g
Mass of chlorine = 325.95 - 184 = 141.95g (Dividing by 35.35; This is approximately 4 Chlorine atoms.
The Formular is WCl₄
In the third compound;
Percentage of tungsten = 50.91 %
Upon solving;
50.91 % = 184
100 % = Total mass
Total mass of compound = 361.42 g
Mass of chlorine = 361.42 - 184 = 177.42 (Dividing by 35.35; This is approximately 5 Chlorine atoms.
The Formular is WCl₅
In the fourth compound;
Percentage of tungsten = 46.39 %
Upon solving;
46.39 % = 184
100 % = Total mass
Total mass of compound = 396.64 g
Mass of chlorine = 396.64 - 184 = 212.64 (Dividing by 35.35; This is approximately 6 Chlorine atoms.
The Formular is WCl₆