1 What is neutralization? Write an equation for the neutralization of HCI by NaOH. 2 Calculate the H+ ion concentration of orange juice with pH = 3.35? 3 What is titration? Why is it important to rinse the burette and pipette with the solution they will eventually contain? 4 In an acid-base titration 50.0 mL of a solution of sodium hydroxide is neutralized by exactly 1250 mL of sulfunc acid of concentration 0.500 mol/L H2SO4 (aq) + 2NaOH (aq)-> Na2SO4 (aq) + 2H20 (1) What is the concentration, in moll, of the sodium hydroxide solution? 5 What is the criteria for choosing an indicator in acid-base titration?
1) Neutralization is a chemical reaction in which an acid and a base react to form a salt and water. The reaction involves the transfer of H+ ions from the acid to the OH- ions from the base.
The equation for the neutralization of HCI (hydrochloric acid) by NaOH (sodium hydroxide) is:
HCl + NaOH -> NaCl + H2O
2) The pH of a solution is a measure of its acidity or alkalinity. The H+ ion concentration can be calculated using the formula: H+ ion concentration = 10^(-pH)
In this case, if the pH of orange juice is 3.35, then the H+ ion concentration can be calculated as:
H+ ion concentration = 10^(-3.35)
3) Titration is a laboratory technique used to determine the concentration of a substance in a solution by reacting it with a solution of known concentration. It involves the gradual addition of a solution of known concentration (titrant) to a solution of unknown concentration (analyte) until the reaction between the two is complete.
It is important to rinse the burette and pipette with the solution they will eventually contain to ensure that there are no contaminants or residual substances that could potentially affect the accuracy of the titration results.
4) The balanced equation for the reaction is:
H2SO4 (aq) + 2NaOH (aq) -> Na2SO4 (aq) + 2H2O (l)
From the balanced equation, it can be seen that 2 moles of NaOH react with 1 mole of H2SO4.
Given that the concentration of H2SO4 is 0.500 mol/L and the volume used is 1250 mL (or 1.25 L), the moles of H2SO4 can be calculated as:
moles of H2SO4 = concentration x volume = 0.500 mol/L x 1.25 L = 0.625 moles
Since the stoichiometric ratio between H2SO4 and NaOH is 1:2, the moles of NaOH can be calculated as:
moles of NaOH = 0.625 moles x (2 moles NaOH / 1 mole H2SO4) = 1.25 moles
Therefore, the concentration of the sodium hydroxide solution is 1.25 mol/L.
5) The criteria for choosing an indicator in an acid-base titration are:
- The indicator should undergo a distinct color change at or near the equivalence point (the point at which stoichiometrically equivalent amounts of the acid and base have reacted).
- The color change should occur over a narrow pH range, so that the point of color change corresponds to the equivalence point.
- The indicator should not react with the analyte or titrant, as this could affect the accuracy of the results.
- The indicator should be added in small quantities, as excessive amounts can introduce errors in the titration.
1. Neutralization is a chemical reaction that occurs when an acid and a base react to form a salt and water. It involves the transfer of protons (H+) from the acid to the base, resulting in the balance of acidic and basic properties. The equation for the neutralization of HCI by NaOH is:
HCl (aq) + NaOH (aq) -> NaCl (aq) + H2O (l)
2. To calculate the H+ ion concentration of orange juice with a pH of 3.35, you can use the formula:
[H+] = 10^(-pH)
So, [H+] = 10^(-3.35) = 4.466 x 10^(-4) M (mol/L).
3. Titration is a laboratory technique used to determine the concentration of a substance in a solution by reacting it with a solution of known concentration. It involves the slow addition of one solution (titrant) to another solution (analyte) until the reaction is complete, usually indicated by a color change or other physical change.
It is important to rinse the burette and pipette with the solution they will eventually contain because it helps to eliminate any remaining impurities or contaminants that could affect the accuracy of the titration. Rinsing ensures that the titrant and analyte are the only substances involved in the reaction and minimizes any potential errors.
4. In the given acid-base titration, H2SO4 (sulfuric acid) reacts with NaOH (sodium hydroxide) in a 1:2 molar ratio. The balanced equation for this reaction is:
H2SO4 (aq) + 2NaOH (aq) -> Na2SO4 (aq) + 2H2O (l)
We are given the concentration of the sulfuric acid solution, which is 0.500 mol/L. From the stoichiometry of the reaction, we can determine the moles of NaOH used:
Moles of H2SO4 = concentration of H2SO4 x volume of H2SO4 (in L)
Moles of NaOH = moles of H2SO4 / 2 (due to mole ratio)
Given:
Volume of H2SO4 = 1250 mL = 1250/1000 = 1.25 L
Moles of H2SO4 = 0.500 mol/L x 1.25 L = 0.625 mol
Moles of NaOH = 0.625 mol / 2 = 0.3125 mol
The concentration of the sodium hydroxide solution can now be calculated:
Concentration of NaOH solution = Moles of NaOH / Volume of NaOH (in L)
Concentration of NaOH solution = 0.3125 mol / 0.0500 L = 6.25 mol/L
Therefore, the concentration of the sodium hydroxide solution is 6.25 mol/L.
5. The criteria for choosing an indicator in acid-base titration are as follows:
- The indicator should change its color sharply and quickly at the equivalence point of the titration. This allows for accurate determination of the point where the reaction is complete.
- The indicator's color change should occur within a suitable pH range, ensuring that it is sensitive to the pH changes during the titration but does not change color prematurely or persistently.
- The indicator should be stable, so it does not undergo any chemical reactions or changes during the titration, which could affect the accuracy of the results.
- The indicator should be available in sufficient quantity and at a reasonable cost.
Examples of indicators commonly used in acid-base titrations include phenolphthalein, methyl orange, bromothymol blue, and litmus.