A substance is dissolved in water, and the temperature of the surroundings decreases. Is this process exothermic or endothermic?
1 answer:
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Answer :
(1) The number of valence electrons present in the compound is, 20
(2) The number of bonded electrons present in the compound is, 16
(3) The number of lone pair electrons present in the compound is, 4
(4) The number of single bonds present in the compound is, 8
Explanation :
Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.
In the Lewis-dot structure the valance electrons are shown by 'dot'.
The given molecule is,
As we know that carbon has '4' valence electrons, hydrogen has '1' valence electrons and oxygen has '6' valence electrons.
Therefore, the total number of valence electrons in = 2(4) + 6(1) + 6 = 20
According to Lewis-dot structure, there are 16 number of bonding electrons and 4 number of non-bonding electrons or lone pair of electrons.
The Lewis-dot structure of is shown below.
20 mL of an approximately 10% aqueous solution of ethylamine, CH3CH2NH2, is titrated with 0.3000 M aqueous HCl. Which indicator would be most suitable for this titration? The pKa of CH3CH2NH3+ is 10.75.
Answer:
Bromocresol green, color change from pH = 4.0 to 5.6
Explanation:
The equation for the reaction is as follows:
+
⇄
Given that concentration of = 10%
i.e 10 g of in 100 ml solution
molar mass = 45.08 g/mol
number of moles =
= 0.222 mol
Molarity of = 0.222 ×
= 2.22 M
However, number of moles of in 20 mL can be determined as:
number of moles of = 20 mL × 2.22 M
=
Concentration of =
= 2.22 M
Similarly, The pKa Value of is given as 10.75
pKb value will be: 14 - pKa
= 14 - 10.75
= 3.25
Finally, the pH value at equivalence point is:
pH=
pH =
pH = 5.21
∴
The indicator that is best fit for the given titration is Bromocresol Green Color change from pH between 4.0 to 5.6.