A 0.2128 M solution of NaOH is used to titrate 37.00 mL of 0.1988 M HI. (Assume that volumes ar

step 1 So our titration is between a strong acid and a strong base. So our net ionic equation is just g

A 0.2128 M solution of NaOH is used to titrate 37.00 mL of...

A $0.2128 M$ solution of $\mathrm{NaOH}$ is used to titrate $37.00 \mathrm{~mL}$ of $0.1988 \mathrm{M}$ HI. (Assume that volumes are additive.) (a) Write a balanced net ionic equation for the reaction that takes place during the titration. (b) What are the species present at the equivalence point besides $\mathrm{H}_{2} \mathrm{O}$ and the $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ that result from the ionization of water? (c) What volume of $\mathrm{NaOH}$ is required to reach the equivalence point? (d) What is the $\mathrm{pH}$ of the solution before any $\mathrm{NaOH}$ is added? (e) What is the $\mathrm{pH}$ of the solution halfway to the equivalence point (half-neutralization)? (f) What is the pH of the solution at the equivalence point?

A $0.2128 M$ solution of $\mathrm{NaOH}$ is used to titrate $37.00 \mathrm{~mL}$ of $0.1988 \mathrm{M}$ HI.
(Assume that volumes are additive.)
(a) Write a balanced net ionic equation for the reaction that takes place during the titration.
(b) What are the species present at the equivalence point besides $\mathrm{H}_{2} \mathrm{O}$ and the $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ that result from the ionization of water?
(c) What volume of $\mathrm{NaOH}$ is required to reach the equivalence point?
(d) What is the $\mathrm{pH}$ of the solution before any $\mathrm{NaOH}$ is added?
(e) What is the $\mathrm{pH}$ of the solution halfway to the equivalence point (half-neutralization)?
(f) What is the pH of the solution at the equivalence point?

Key Concepts

pH Calculation

pH calculation involves using the concentration of hydronium ions or hydroxide ions to determine the acidity or basicity of a solution. This is crucial in titrations, especially at different stages like before titration, at the half-equivalence point, and at the equivalence point, where the pH gives insights into the progress and nature of the reaction.

Half-Equivalence Point

The half-equivalence point in a titration is when half of the analyte has been neutralized by the titrant. This point is particularly useful because, in acid-base titrations, the pH at the half-equivalence point is equal to the pKa of the weak acid (or pKb of the weak base) involved, if the reaction involves a weak acid or base.

Stoichiometry in Titrations

Stoichiometry in titrations involves calculating the number of moles of reactants and products using concentration and volume. This is essential for determining the equivalence point where the moles of titrant and analyte are in a stoichiometric ratio defined by the balanced chemical reaction.

Molarity and Volume Relationships

Molarity and volume are used to calculate the number of moles of substances in a solution. In titrations, knowing the molarity (concentration) of the solutions and precisely measuring the volume allows for accurate determination of the amounts of reactants, which is essential for reaching the desired end point in the titration process.

Net Ionic Equation

The net ionic equation eliminates spectator ions that do not participate in the chemical change, focusing only on the species that undergo a reaction. In strong acid-strong base titrations, the net ionic equation usually highlights the proton transfer between H+ and OH- to form water.

Acid-Base Reaction

Acid-base reactions involve the transfer of protons between species, typically resulting in the formation of water and a salt. In titrations, a strong acid is often reacted with a strong base, leading to complete dissociation and a reaction that is predictable and well-understood due to the full ionization of the reactants.

Titration

Titration is an analytical technique used to determine the concentration of a solution by reacting it with a solution of known concentration. This method involves gradually adding one reactant to another until the reaction reaches its end point or equivalence point, where the amount of titrant is stoichiometrically equivalent to the analyte in the sample.

Equivalence Point

The equivalence point in a titration is reached when the number of moles of titrant added equals the number of moles of the analyte based on the stoichiometry of the reaction. At this point, the reactants have reacted completely in the defined chemical reaction, and additional titrant will start to change the pH of the solution dramatically.

Transcript

00:01 So our titration is between a strong acid and a strong base.

00:06 So our net ionic equation is just going to be h plus plus oh minus gives us water.

00:13 And at the equivalence point, other than water, we'll just have our two spectator ions also present.

00:22 And then we're going to see if we can figure out how much n -a -o -h we need to get to our equivalence point.

00:28 So let's start with our information about our strong acid.

00:34 Molar.

00:36 We'll multiply that by its liters and we'll see that we had 7 .36 times 10 of the minus 3 moles of our strong acid.

00:48 Therefore we must have also reacted that same amount of our strong base, so our oh -h -minus.

00:58 And then if we take that and divide it by the molarity, we'll get our volume.

01:05 Okay, because molarity is moles per liter.

01:09 So that will give us 0 .03457 liters or 34 .57 milliliters.

01:23 Okay, so before the titration occurs, all we have is our strong acid.

01:29 Our h plus concentration was given as .1988 molar.

01:37 So if we take minus the log of that, we'll get our ph, which is 0 .7 016.

01:52 Halfway to the equivalence point, one half of the moles of h plus have reacted.

02:01 So we are left with half of our moles left, and we've added half the volume of our oh minus...

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