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serious [3.7K]
3 years ago
12

g Calculate the pOH of a solution that results from mixing 23.3 mL of 0.16 M trimethylamine ((CH3)3N) with 44.1 mL of 0.15 M (CH

3NH3Cl. The Kb value for (CH3)3N is 6.5 x 10-5.
Chemistry
1 answer:
hichkok12 [17]3 years ago
6 0

Answer:

pOH = 5.961

Explanation:

To find the pH of a weak base we can use Henderson-Hasselbalch equation for weak bases:

pOH = pKb + log [(CH₃)₃NHCl] / [(CH₃)₃N]

<em>Where pKb is -log Kb = 4.187 and [] could be taken as moles of each specie.</em>

<em />

<em>Moles (CH₃)₃NHCl:</em>

0.0441L * (0.15mol/L) = 6.615x10⁻³moles

<em>Moles (CH₃)₃N:</em>

0.0233L * (0.16mol/L) = 3.728x10⁻³moles

And pOH is:

pOH = pKb + log [(CH₃)₃NHCl] / [(CH₃)₃N]

pOH = 4.187 + log [6.615x10⁻³moles] / [3.728x10⁻³moles]

<h3>pOH = 5.961</h3>

<em />

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In an isolated system:
ipn [44]

Answer:

isolated system (plural isolated systems) (physics) A system that does not interact with its surroundings. Depending on context this may mean that its total energy and/or momentum stay constant.

Explanation:

An isolated system is a thermodynamic system that cannot exchange either energy or matter outside the boundaries of the system. ... The system may be enclosed such that neither energy nor mass may enter or exit.

is there both?

7 0
3 years ago
In the laboratory you dissolve 13.9 g of potassium phosphatein a volumetric flask and add water to a total volume of 250mL.
tensa zangetsu [6.8K]

Answer:

Molarity of the solution? 0,262 M.

Concentration of the potassium cation? 0,786 M.

Concentration of the phosphate anion? 0,262 M.

Explanation:

Potassium phosphate (K₃PO₄; 212,27 g/mol) dissolves in water thus:

K₃PO₄ → 3 K⁺ + PO₄³⁻ <em>(1)</em>

Molarity is an unit of chemical concentration given in moles of solute (K₃PO₄) per liters of solution.

There are 250 mL of solution≡0,25 L

The moles of K₃PO₄ are:

13,9 g of K₃PO₄ ×\frac{1mol}{212,27 g} = 0,0655 moles of K₃PO₄

The molarity of the solution is:

\frac{0,0655 moles}{0,25L} = 0,262 M

In (1) you can see that 1 mole of K₃PO₄ produces 3 moles of potassium cation. The moles of potassium cation are:

0,0655 moles×3 = 0,1965 moles

The concentration is:

\frac{0,1965 moles}{0,25L} = 0,786 M

The moles of K₃PO₄ are the same than moles of PO₄³⁻, thus, concentration of phosphate anion is the same than concentration of K₃PO₄. 0,262 M

I hope it helps!

4 0
3 years ago
A gas sample has a temperature of 22c with an unknown volume. The same gas has a volume of 456 mL when the temperature is 86c wi
Mkey [24]

The initial volume is 116.65 mL

<u>Explanation:</u>

<u />

Given:

Temperature, T₁ = 22°C

T₂ = 86°C

Volume, V₂ = 456 m

V₁ = ?

According to Charle's law:

\frac{V_1}{T_1} = \frac{V_2}{T_2}

Substituting the values:

\frac{V_1}{22} =\frac{456}{86} \\\\V_1 = \frac{456 X 22}{86} \\\\V_1 = 116.65 mL

Therefore, the initial volume is 116.65 mL

3 0
3 years ago
A 1.50-kilogram ball is attached to the end of a 0.520-meter string and swung in a circle. The velocity of the ball is 9.78 m/s.
Sedaia [141]

Answer:

F centripetal force (tension) = 275.9  N

Explanation:

Given data:

Mass = 1.50 kg

Radius = 0.520 m

Velocity of ball = 9.78 m/s

Tension = ?

Solution:

F centripetal force (tension) =  m.v² / R

F centripetal force (tension) = 1.50 kg . (9.78 m/s)² / 0.520 m

F centripetal force (tension) = 1.50 kg . 95.65 m²/s² / 0.520 m

F centripetal force (tension) = 143.5 kg. m²/s² / 0.520 m

F centripetal force (tension) = 275.9  N

7 0
3 years ago
How many photons are produced in a laser pulse of 0.497 J at 469 nm?
dimulka [17.4K]
<span>E=hν</span> where E is the energy of a single photon, and ν is the frequency of a single photon. We recall that a photon traveling at the speed of light c and a frequency ν will have a wavelength λ given by <span>λ=<span>cν</span></span>λ will have an energy given by <span>E=<span><span>hc</span>λ</span></span><span>λ=657</span> nm. This will be <span>E=<span><span>(6.626×<span>10<span>−34</span></span>)(2.998×<span>108</span>)</span><span>(657×<span>10<span>−9</span></span>)</span></span>=3.0235×<span>10<span>−19</span></span>J</span> So we now know the energy of one photon of wavelength 657 nm. To find out how many photons are in a laser pulse of 0.363 Joules, we simply divide the pulse energy by the photon energy or <span>N=<span><span>E<span>pulse </span></span><span>E<span>photon</span></span></span>=<span>0.363<span>3.0235×<span>10<span>−19</span></span></span></span>=1.2×<span>1018</span></span>So there would be <span>1.2×<span>1018</span></span><span> photons of wavelength 657 nm in a pulse of laser light of energy 0.363 Joules.</span>
7 0
3 years ago
Read 2 more answers
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