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
If a hypothesis is not contradicted after a lot of testing it may be considered a law
Answer: Paramagnetism is most easily observed in the salts of some of the first row transition metals (manganese through nickel). The se metal ions have unpaired electrons in degenerate d orbitals as predicted by Hund's rule and thus exhibit paramagnetism.
Explanation: METALS ARE ELECTRONS
AND PARAMAGNETIC OBSERVES SALT FORST ROWS ONLY
Answer:
Explanation:
The oxidation reduction reactions are called redox reaction. These reactions are take place by gaining or losing the electrons and oxidation state of elements are changed.
Oxidation:
Oxidation involve the removal of electrons and oxidation state of atom of an element is increased.
Reduction:
Reduction involve the gain of electron and oxidation number is decreased.
Consider the following reactions.
4KI + 2CuCl₂ → 2CuI + I₂ + 4KCl
the oxidation state of copper is changed from +2 to +1 so copper get reduced.
CO + H₂O → CO₂ + H₂
the oxidation state of carbon is +2 on reactant side and on product side it becomes +4 so carbon get oxidized.
Na₂CO₃ + H₃PO₄ → Na₂HPO₄ + CO₂ + H₂O
The oxidation state of carbon on reactant side is +4. while on product side is also +4 so it neither oxidized nor reduced.
H₂S + 2NaOH → Na₂S + 2H₂O
The oxidation sate of sulfur is -2 on reactant side and in product side it is also -2 so it neither oxidized nor reduced.
Oxidizing agents:
Oxidizing agents oxidize the other elements and itself gets reduced.
Reducing agents:
Reducing agents reduced the other element are it self gets oxidized
Answer:
0.20M
Explanation:
Molarity (by definition) = moles / Volume in Liters
∴Molarity = 0.030mol/0.15Liter = 0.20M
