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boyakko [2]
2 years ago
6

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M methylamine, CH3NH2, with 20.00 mL of 0.10 M methylammonium c

hloride, CH3NH3Cl? Assume that the volume of the solutions are additive and that Kb = 3.70 × 10-4 for methylamine
Chemistry
1 answer:
olya-2409 [2.1K]2 years ago
4 0

Answer:

pH=10.97

Explanation:

the solution of methyl amine with methylammonium chloride will make a buffer solution.

The pH of buffer solution can be obtained using Henderson Hassalbalch's equation, which is:

pOH=pKb+log\frac{[salt]}{[base]}

pH = 14- pOH

Let us calculate pOHpOH=3.43+ (-0.397)=3.03

pH=14-pOH=14-3.03=10.97

[Salt] = [methylammonium chloride] = 0.10 M (initial)

After adding base

[salt] = \frac{molarityXvolume}{finalvolume}=\frac{0.1X20}{(20+50)}= 0.0286M

[base] = [Methylamine]=0.10

After mixing with salt

[base]= \frac{molarityXvolume}{finalvolume}=\frac{0.1X50}{(20+50)}= 0.0714M

pKb= -log[Kb]= 3.43

Putting values

pOH = 3.43+log(\frac{[0.0286]}{0.0714}

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Why does 5060 have three significant figures?
Morgarella [4.7K]
<h2>5060 have three significant figures : Explanation given below </h2>

Explanation:

Significant figures

The significant figures (also known as the significant digits and decimal places) of a number are digits that possess certain  meaning .

It  includes all digits except: zeros

Rules to find significant figures

1.All non-zero digits are considered significant. For example, 23  has two significant figures.

2.Zeros in between two non-zero digits are significant: like in 202.1201  has seven significant figures.

3.Zeros to the left of the significant figures are not significant. For example, .000021 has two significant figures, zeros have no value .

4.Zeros to the right of the significant figures are significant.

That is the reason in number 5060 , it has 3 significant figures .

3 0
2 years ago
If 36.9 mL of B2H6 reacted with excess oxygen gas, determine the actual yield of B2O3 if the percent yield of B2O3 was 75.7%. (T
zhuklara [117]

Answer: The actual yield of B_2O_3 is 60.0 g

Explanation:-

The balanced chemical reaction :

B_2H_6(l)+3O_2(g)\rightarrow B_2O_3(s)+3H_2O(l)

Mass of B_2H_6 =Density\times Volume=1.131g/ml\times 36.9ml=41.7g

\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}    

\text{Moles of} B_2H_6=\frac{41.7g}{27.668g/mol}=1.51moles

According to stoichiometry:

1 mole of B_2H_6 gives = 1 mole of B_2O_3

1.51 moles of B_2H_6 gives =\frac{1}{1}\times 1.51=1.51 moles of B_2O_3

Theoretical yield of B_2O_3=moles\times {Molar mass}}=1.14mol\times 69.62g/mol=79.3g

Percent yield of B_2O_3= 75.7\%

\%\text{ yield}=\frac{\text{Actual yield}}{\text{Theoretical yield}}\times 100

75.7\%=\frac{\text{Actual yield}}{79.3}\times 100

{\text{Actual yield}}=60.0g

Thus the actual yield of B_2O_3 is 60.0 g

7 0
2 years ago
Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50 Ti (5.3%). What is the average atomic
zhannawk [14.2K]
(46x8.0)+(47x7.8)+(48x73.4)+(49x5.5)+(50x5.3) = 4792.3

4792.3/100 = 47.923 this is the average atomic mass of Titanium
6 0
2 years ago
2.1. The lithium ion in a 250,00 mL sample of mineral water was
juin [17]

Answer:

11482 ppt of Li

Explanation:

The lithium is extracted by precipitation with B(C₆H₄)₄. That means moles of Lithium = Moles B(C₆H₄)₄. Now, 1 mole of B(C₆H₄)₄ produce the liberation of 4 moles of EDTA. The reaction of EDTA with Mg²⁺ is 1:1. Thus, mass of lithium ion is:

<em>Moles Mg²⁺:</em>

0.02964L * (0.05581mol / L) = 0.00165 moles Mg²⁺ = moles EDTA

<em>Moles B(C₆H₄)₄ = Moles Lithium:</em>

0.00165 moles EDTA * (1mol B(C₆H₄)₄ / 4mol EDTA) = 4.1355x10⁻⁴ mol B(C₆H₄)₄ = Moles Lithium

That means mass of lithium is (Molar mass Li=6.941g/mol):

4.1355x10⁻⁴ moles Lithium * (6.941g/mol) = 0.00287g. In μg:

0.00287g * (1000000μg / g) = 2870μg of Li

As ppt is μg of solute / Liter of solution, ppt of the solution is:

2870μg of Li / 0.250L =

<h3>11482 ppt of Li</h3>

4 0
2 years ago
Complete this equation for the dissociation of the electrolyte NaCl(aq). Omit water from the equation because it is understood t
ella [17]

1. Answer;

Equation;

-NaCl(aq) → Na{+}(aq) + Cl{-}(aq)

Explanation;

-The polar property of water allows ionic compounds such as sodium chloride to dissolve in water. (sodium chloride is an ionic compound).

-Sodium chloride dissociates in water into sodium ions and chloride ions as shown by the equation. Water molecules surrounds the negatively charged chloride ions and positive sodium ions and pulls them away into solution.

2. Answer;

Equation;

Fe(ClO4)3(aq) → Fe 3+(aq) + 3ClO4 - (aq)

Explanation;

Iron (iii) perchlorate (Fe(ClO4)3 dissociates in water into iron (iii) ion and perchlorate ion. Iron (iii) ion is positively charged while the perchlorate ion is negatively charged, they are pulled apart by the polar water molecules, a process called dissociation.

-

5 0
2 years ago
Read 2 more answers
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