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skelet666 [1.2K]
3 years ago
7

The acid-dissociation constant of hydrocyanic acid (hcn) at 25.0 °c is 4.9 ⋅ 10−10. what is the ph of an aqueous solution of 0.0

80 m sodium cyanide (nacn)?
Chemistry
1 answer:
vodomira [7]3 years ago
5 0
According to the reaction equation:

and by using ICE table:

              CN-  + H2O ↔ HCN  + OH- 

initial  0.08                        0          0

change -X                        +X          +X

Equ    (0.08-X)                    X            X

so from the equilibrium equation, we can get Ka expression

when Ka = [HCN] [OH-]/[CN-]

when Ka = Kw/Kb

               = (1 x 10^-14) / (4.9 x 10^-10)

               = 2 x 10^-5

So, by substitution:

2 x 10^-5 = X^2 / (0.08 - X)

X= 0.0013

∴ [OH] = X = 0.0013 

∴ POH = -㏒[OH]

            = -㏒0.0013

            = 2.886 

∴ PH = 14 - POH

         = 14 - 2.886 = 11.11
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What is the ph of a 0.0055 m ha (weak acid) solution that is 8.2% ionized?
Trava [24]
Answer is: pH value of weak is 3.35.
Chemical reaction (dissociation): HA(aq) → H⁺(aq) + A⁻(aq).
c(HA) = 0.0055 M.
α = 8.2% ÷ 100% = 0.082.
[H⁺] = c(HA) · α.
[H⁺] = 0.0055 M · 0.082.
[H⁺] = 0.000451 M.
pH = -log[H⁺].
pH = -log(0.000451 M).
pH = 3.35.
pH (potential of hydrogen) is a numeric scale used to specify the acidity or basicity <span>an aqueous solution.</span>
3 0
3 years ago
Fe2O3 + CO --&gt; Fe + CO2
satela [25.4K]

Answer:

The answer to your question is

1.-Fe₂O₃

2.- 280 g

3.- 330 g

Explanation:

Data

mass of CO = 224 g

mass of Fe₂O₃ = 400 g

mass of Fe = ?

mass of CO₂

Balanced chemical reaction

                       Fe₂O₃   + 3CO    ⇒  2Fe  +   3CO₂

1.- Calculate the molar mass of Fe₂O₃ and CO

Fe₂O₃ = (56 x 2) + (16 x 3) = 160 g

CO = 12 + 16 = 28 g

2.- Calculate the proportions

theoretical proportion Fe₂O₃ /3CO = 160/84 = 1.90

experimental proportion Fe₂O₃ / CO = 400/224 = 1.78

As the experimental proportion is lower than the theoretical, we conclude that the Fe₂O₃ is the limiting reactant.

3.-     160 g of Fe₂O₃  --------------- 2(56) g of Fe

         400 g of Fe₂O₃ ---------------  x

         x = (400 x 112) / 160

        x = 280 g of Fe

4.-      160 g of Fe₂O₃  --------------- 3(44) g of CO₂

          400 g of Fe₂O₃  --------------  x

          x = (400 x 132)/160

         x = 330 gr

3 0
3 years ago
Which of the species below can act as a lewis base? bf3 nf3 oh− alcl3?
IRINA_888 [86]
Among BF₃, NF₃, OH⁻ and ALCl₃ both NF₃ and OH⁻ acts as a lewis base.

Explaination:
According to lewis theory of acid and base, base is a specie which has either lone pair of electrons or is negatively charged. So, in the given compounds Nitrogen trifluoride contain lone pair of electron on nitrogen and Hydroxide contains a negative charge on oxygen. And botha are capable to donate these electrons to a lewis acid (electrophiles).

6 0
3 years ago
Consider the reaction between hydrogen gas and chlorine gas to form hydrogen chloride gas in a closed cylinder with a movable pi
d1i1m1o1n [39]

Answer:

In this case, the system doesn't be affected by the pressure change. This means that nothing will happen

Explanation:

We can answer this question applying the Le Chatelier's Principle. It says that changes on pressure, volume or temperature of an equilibrium reaction will change the reaction direction until it returns to the equilibrium condition again.

The results of these changes can define as:

Changes on pressure: the reaction will move depending the quantity of moles on each side of the reaction

Changes on temperature: The reaction will move depending on if it's endothermic or exothermic

Changes on volume: The reaction will move depending the limit reagent  and the quantity of moles on each side of the reaction

In the exercise, they mention a change on pressure of the system at constant temperature (that means the temperature doesn't change). As Le Chatelier Principle's says, we must analyze what happens if the pressure increase or decrease. If pressure increase the reaction will move on the side that have less quantity of moles, otherwise, if the pressure decreases the reaction will move to the side that have more quantity of moles. In this case, we can see that both sides of the equation have the same number of moles (2 for the reactants and 2 for the products). So, in this case, we can conclude that, despite the change on pressure (increase or decrease), nothing will happen.

3 0
3 years ago
Mountains and valleys are some of the features found in the layer of rock at Earth's surface called the
loris [4]

Answer:

Narrow

Explanation:

Narrow

5 0
3 years ago
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