Determine the number of protons and neutrons in plutonium-239 and write its symbol in the form azx.
2 answers:
Explanation:
Atomic number of an atom means the sum of total number of protons present in an atom.
Mass number is the sum of total number of protons and neutrons present in an atom.
And, when we write the symbol of an atom then it is represented like this , where "a" represents the mass number of the atom and "z" represents the number of protons.
Therefore, in plutonium-239 it is shown that mass number is 239 and atomic number of a plutonium atom is 94. Now, calculate its number of neutrons as follows.
Mass number = no. of protons + no. of neutrons
239 = 94 + no. of neutrons
no. of neutrons = 239 - 94
= 145
Thus, we can conclude that in plutonium-239 number of protons is 94, number of neutrons is 145 and its symbol is .
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Answer:
pH = 8.24
Explanation:
Nitrous acid (HNO₂) reacts with KOH, thus:
HNO₂ + KOH → KNO₂ + H₂O
Moles of HNO₂ are:
0.0257mL ₓ (0.370mol / L) = 0.00951moles.
In equivalence point, the complete moles of nitrous acid reacts with KOH producing potassium nitrite. There are needed:
0.00951mol ₓ (1L / 0.491mol) = 0.01937L ≡ 19.4mL of 0.491M KOH to reach equivalence point.
Total volume in equivalence point is: 19.4mL + 25.7mL = <em>45.1mL</em>
Potassium nitrite is in equilibrium with water, thus:
NO₂⁻ + H₂O ⇄ HNO₂ + OH⁻
Where equilibrium constant, Kb, is defined as:
Kb = 1.41x10⁻¹¹ =
In equilibrium, molarity of each compound are:
[NO₂⁻]: 0.00951mol/0.00451L - X = 0.211M - X
[HNO₂]: X
[OH⁻]: X
<em>Where X is reaction coordinate</em>
Replacing in Kb:
1.41x10⁻¹¹ =
0 = X² + 1.41x10⁻¹¹X - 2.97x10⁻¹²
Solving for X:
X = -1.72x10⁻⁶ <em>FALSE ANSWER. There is no negative concentrations.</em>
X = 1.72x10⁻⁶. <em>Right answer.</em>
That means:
[OH⁻]: 1.72x10⁻⁶M
As pOH is -log [OH⁻] and pH = 14-pOH:
pOH = 5.76; <em>pH = 8.24</em>