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kakasveta [241]
3 years ago
5

Benzoic acid is a weak monoprotic acid. It has a pKa of 4.20. A student transferred 25.00mL of 0.126M benzoic acid into a beaker

. The student then added 20.00mL of distilled water into the beaker. Calculate the equilibrium pH for this benzoic acid solution.
Chemistry
1 answer:
Andru [333]3 years ago
5 0

Answer:

pH of the benzoic acid solution = 3.35

Explanation:

Benzoic acid is a weak monoprotic acid

  pKa = 4.2

⇒ Ka = 6.3 x 10⁻⁵

                                  C₆H₅COOH ⇄ C₆H₅COO⁻ + H⁺

Initial concentration      C molar             0                0

At equilibrium               (c - cα)               cα               cα

                      Acid dissociation constant Ka = \frac{c\alpha X c\alpha  }{c - c\alpha }

                                              ⇒          6.3 x 10⁻⁵ = α²c ................(1)

(for weak electrolyte 1 -α = 1)

Concentration of benzoic acid C = 25 x 0.126 x 10⁻³ = 0.00315 molar

                  From eqn (1)

                          α² = \frac{6.3 X 10^{-5} }{0.00315}

                    ⇒  α = √(\frac{6.3 X 10^{-5} }{0.00315} )

                    ⇒  α = 0.14

So concentration of H⁺ ion = 0.14 x 0.00315 = 0.000441

pH = - log 0.000441 = 3.35    

We not considered H⁺ concentration of water because pH  < 7                  

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For any given element, ionization energy increases as subsequent electrons are removed. For example, the energy required to remove an electron from neutral chlorine is 1251 kJ/mol. ... An even sharper increase in ionization energy is witnessed when inner-shell, or core, electrons are removed.

Hope it helps :)

6 0
2 years ago
How many grams of glucose are needed to prepare 400. g of a 2.00% (m/m) glucose solution g?
Dominik [7]
The grams   of glucose  are  needed  to  prepare  400g  of  a 2.00%(m/m)  glucose  solution  g  is  calculated  as  below

=% m/m =mass  of the solute/mass  of  the  solution  x100

let mass of   solute  be represented  by  y
mass  of solution = 400 g
 % (m/m) = 2% = 2/100

 grams  of  glucose  is  therefore =2/100 =  y/400
by cross  multiplication

100y = 800
divide   both side  by  100

y= 8.0 grams



5 0
3 years ago
For the following systems at equilibrium C: CaCO3(s) ⇌ CaO(s)+CO2(g) ΔH=+178 kJ/mol D: PCl3(g)+Cl2(g) ⇌ PCl5(g) ΔH=−88 kJ/mol cl
Rama09 [41]

Explanation:

C: CaCO_3(s)\rightleftharpoons CaO(s)+CO_2(g)ΔH=+178 kJ/mol

For an endothermic reaction, heat is getting absorbed during a chemical reaction and is written on the reactant side.

A+\text{heat}\rightleftharpoons B

Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.  This principle states that if there is any change in the variables of the reaction, the equilibrium will shift in the direction to minimize the effect.

Treat heat as a reactant and on increasing a reactant at equilibrium, shifts the reaction in the forward direction.

Increase temperature →  increase in heat → forward direction

Decrease temperature →  decease in heat → backward direction

System C - Increase temperature : Reaction will move forward

System C - Decrease temperature : Reaction will move backward

D: PCl_3(g)+Cl_2(g)\rightleftharpoons PCl_5(g) ΔH=−88 kJ/mol

The total enthalpy of the reaction comes out to be negative .

The temperature of the surrounding will increase.

For an exothermic reaction, heat is released during a chemical reaction and is written on the product side.

A\rightleftharpoons B+\text{ heat}

Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.  This principle states that if there is any change in the variables of the reaction, the equilibrium will shift in the direction to minimize the effect.

Treat heat as a product and on increasing a product at equilibrium, shifts the reaction in the backward direction.

Increase temperature →  increase in heat → backward direction

Decrease temperature →  decease in heat → forward direction

System D - Increase temperature : Reaction will move backward

System D - Decrease temperature : Reaction will move forward

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2 years ago
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mel-nik [20]

Answer: C. no new substances are formed<span>
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5 0
2 years ago
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Please help, I’m a bit confused, lol
Mashutka [201]

Explanation:

option A skeleton system is correct option

hope this helps you !

4 0
2 years ago
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