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mixas84 [53]
2 years ago
5

Calculate the ph at the equivalence point for the titration of 0. 22 m hcn with 0. 22 m naoh. (ka = 4. 9 × 10^–10 for HCN).

Chemistry
1 answer:
denis-greek [22]2 years ago
4 0

The pH at the equivalence point for the titration of 0. 22 m HCN with 0. 22 m NaOH is 11.17

Calculation,

Concentration of NaCN = 0. 22 m/ 2 = 0.11 M ( at equal volumes of acid and base will be used).

The equilibrium is ,

HCN +H_{2} O  → H^{+} + CN^{-}

C(1-x)              Cx      Cx

Where x , is the degree of hydrolysis and

K_{h} = Cx^{2}/(1-x)

We know that K_{h} = K_{w}/K_{a} = 1 ×10^{-14}/4. 9 ×10^{-10} =  2.04×10^{-5}

K_{h} =  Cx^{2} =   2.04×10^{-5}  = 0.11 M×x^{2}

x^{2} =  2.04×10^{-5}/0.11 M

x = 1.36×10^{-2}

[OH^{-} ] = Cx =  1.36×10^{-2} × 0.11 M = 0.15×10^{-2}

[H^{+} ] =  1 ×10^{-14}/ 0.15×10^{-2} = 6.66×10^{-12}

pH = -㏒[H^{+} ] = -㏒6.66×10^{-12} = 11.17

The pH at the equivalence point for the titration is  11.17.

To learn more about  equivalence point

brainly.com/question/14782315

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Which of the following is true for an excess reactant?
kupik [55]

Answer:

C) It is the reactant that is left over after the reaction stops.

Explanation:

The excess reactant is the reactant that is left over after the reaction stops. The extent of the reaction is not determined by this reactant.

A limiting reactant is a reactant that is in short supply within a given reaction.

Such reactants determines the extent of chemical reaction.

  • Limiting reactants are used up in a chemical reaction.
  • The excess reactants remains unchanged after the reaction.
8 0
2 years ago
rank the four gases (air, exhaled air, gas produced from the decomposition of H2O2, gas from decomposition of NaHCO3, in order o
SVEN [57.7K]

Answer: H₂O₂ (94%) > Air (23%) > Exhaled air (13%) > NaHCO₃ (0%)


Initial important note:


Although NaHCO₃ contents oxygen atoms, and you can calculate its compositoin, the resulting gas does not containg pure oxygen gas (O₂). For the comparisson it is not useful to calculate the content of oxygent atoms, but the concentration of O₂ gas. As such, the gas from NaHCO₃ contains 0% of pure O₂, that is why it is ranked last.


1) Air:


Source: internet


Approximate 23%. It is variable, because air is not a pure substance but a mixture of gases, whose compositon is not unique.


2) Exhaled air:


Source: internet.


Approximate 13%. The compositon of the air changes in our lungs, due to the respiration process: we inhale fresh air with around 23% of oxygen, part of this oxygen pass to the cells (lungs - blood - heart - cells) and then it is exhaled with a lower content of air and a greater content of CO₂


3) Air from the decomposition of H₂O₂.


In this case we can do a chemical calculation, since we can state the chemical equation of the reaction:


i) Chemical Equation:


H₂O₂ (g) → H₂ (g) + O₂ (g)


ii) mole ratio of the products 1 mol H₂ : 1 mol O₂


iii) convert moles into mass (grams)


1 mol H₂ × 2 × 1.008 g/mol = 2.016 g


1 mol O₂ × 2 × 15.999 g/mol = 31.998 g


Composition, % = [31.998 g / (2.016 g + 31.998 g) ] × 100 ≈ 94%



4) Air from the decomposition of NaHCO₃:


i) chemical equation:


2 NaHCO₃(s) → Na₂CO₃(s) + CO₂(g) + H₂O(g)


ii) mole ratio: take into account only the gases in the products:


1 mol CO₂ (g) : 1 mol H₂O


iii) mass in grams


CO₂: molar mass ia approximately 44.01 g/mol


H₂O: molar mass is approximately 18.02 g/mol


iii) Those gases although have oxygen atoms, do not hae free oxygen gas, which is what we are compariing. That means, that from the decomposition of NaHCO₃ you get 0% oxygen gas.


5) The result is:


H₂O₂ (94%) > Air (23%) > Exhaled air (13%) > NaHCO₃ (0%)

7 0
3 years ago
Read 2 more answers
Classify each amino acid into the following categories. Select the amino acid that fits best in each category. Each amino acid w
mel-nik [20]

Answer:

1. Lysine

2. Aspartic acid

3. Serine

4. Alanine

5. Tryptophan

Explanation:

Amino acids are biomolecules that contain two functional groups and one R side chain. The two functional groups are: carboxyl group and amino group.

The α-amino acids are the amino acids in which the two functional groups and the R side chain are attached to the α-carbon of the amino acid. They are total 22 α-amino acids.

1. A basic amino acid: Lysine is a positively charged, polar basic amino acid with a lysyl side chain.

2. An acidic amino acid: Aspartic acid is a negatively charged, polar acidic amino acid with an acidic carboxymethyl group.

3. A neutral polar amino acid: Serine is a polar and neutral amino acid with a hydroxymethyl group.

4. A non-polar aliphatic amino acid: Alanine is an aliphatic, nonpolar and neutral amino acid with a methyl side chain.

5. An aromatic amino acid: Tryptophan is an aromatic, nonpolar and neutral amino acid with an indole side chain.

3 0
3 years ago
The number 4012 has how many significant figures?​
grandymaker [24]

Answer:

8 figures.

Explanation:

3 0
2 years ago
An excess of oxygen reacts with 451.4 g of lead, forming 374.7 g of lead(II) oxide. Calculate the percent yield of the reaction.
Stels [109]

Answer: The percent yield of the reaction is 77.0 %

Explanation:

2Pb+O_2\rightarrow 2PbO

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}

\text{Number of moles of lead}=\frac{451.4g}{207.2g/mol}=2.18moles

\text{Number of moles of lead oxide}=\frac{374.7g}{223.2g/mol}=1.68moles

According to stoichiometry:

2 moles of Pb produces = 2 moles of PbO_2

2.18 moles of Pb is produced by=\frac{2}{2}\times 2.18=2.18moles of PbO_2

Mass of PbO_2 =moles\times {\text {Molar mass}}=2.18\times 223.2g/mol=486.6

percent yield =\frac{374.7g}{486.6g}\times 100=77.0\%

3 0
3 years ago
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