When the titration of HCN with NaOH is:
HCN (aq) + OH- (aq) → CN-(aq) + H2O(l)
So we can see that the molar ratio between HCN: OH-: CN- is 1:1 :1
we need to get number of mmol of HCN = molarity * volume
= 0.2 mmol / mL* 10 mL = 2 mmol
so the number of mmol of NaOH = 2 mmol according to the molar ratio
so, the volume of NaOH = moles/molarity
= 2 mmol / 0.0998mL
= 20 mL
and according to the molar ratio so, moles of CN- = 2 mmol
∴the molarity of CN- = moles / total volume
= 2 mmol / (10mL + 20mL ) = 0.0662 M
when we have the value of PKa = 9.31 and we need to get Pkb
so, Pkb= 14 - Pka
= 14 - 9.31 = 4.69
when Pkb = -㏒Kb
4.69 = -㏒ Kb
∴ Kb = 2 x 10^-5
and when the dissociation reaction of CN- is:
CN-(aq) + H2O(l) ↔ HCN(aq) + OH- (aq)
by using the ICE table:
∴ the initials concentration are:
[CN-] = 0.0662 M
and [HCN] = [OH]- = 0 M
and the equilibrium concentrations are:
[CN-] = (0.0662- X)
[HCN] = [OH-]= X
when Kb expression = [HCN][OH-] /[CN-]
by substitution:
2 x 10^-5 = X^2 / (0.0662 - X)
X = 0.00114
∴[OH-] = X = 0.00114
when POH = -㏒[OH]
= -㏒ 0.00114
POH = 2.94
∴PH = 14 - 2.94 = 11.06
Answer:
C. Chemical Energy
Explanation:
The energy that stored in the substance or in compounds is called chemical energy which released when the substance reacts.
A substance is made up of atoms and molecules and chemical energy is present in those atoms or molecules. When a chemical reaction takes place, these energy released from atoms and molecules.
Chemical energy can be released in the form of thermal energy (heat) and mechanical energy (working ability).
Hence, the correct answer is "C. Chemical Energy".
Answer:
4.226×10^8
Explanation:
4.2 ×10^8+2.6×10^6=422600000
or 4.226×10^8
A) number of neutrons in the nucleus... all isotopes of an element contain the same number of protons which is equal to that elements atomic number...
hope this helps!
Raoult's law is stated as<span> the partial </span>vapor pressure<span> of each component in the </span> mixture<span> of ideal liquids is equal to the vapor pressure of the pure component multiplied by its </span>mole fraction<span> in the mixture. Mathematically, it is expressed as
P = Xi Pi
where P= vapor pressure of solution
Xi = mole fraction of i component
Pi = vapor pressure of pure i component.
In present case, P1 = 0.459 atm and n1 = number of mole of ethanol = 0.090
n2 = number of mole of </span><span> naphthalene = 0.01
</span>∴ Mole fraction of ethanol =

=

= 0.9
Thus, vapor pressure of solution = 0.9 X 0.459 = 0.4131 atm.
Answer: <span>The vapor pressure of pure ethanol at 60 °c is 0.459 atm. Raoult's law predicts that a solution prepared by dissolving 10.0 mmol naphthalene (nonvolatile) in 90.0 mmol ethanol will have a vapor pressure of
0.4131 atm.</span>