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CHEM 1000H Lecture Notes - Lecture 4: Sodium Hydroxide

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violetwasp748
21 Jan 2016
School
Trent University
Department
Chemistry
Course
CHEM 1000H
Professor
Goring Gillian

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Document Summary

Answer to question: there is an excellent explanation in the beginning of the lab manual. Part b step a. Balanced equation naoh(aq) + ha(a) ! - always get water and salt in this type of reactant. First step: find moles of sodium hydroxide. - concentration used * amount used. Litres cancel out, give you moles. - number of moles of naoh = 0. 200 mol/l * 0. 02500l = 0. 005mol. Step 2: find moles of ha. - 1:1 ratio, therefore there are 0. 00500 moles of ha as well. - 0. 005mol / what you titrated. Part b step b.

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Related Questions

DATA FROM EXPERIMENT:

MASS OF WEIGHING PAPER = 0.3670 g
MASS OF WEIGHING PAPER + Al FOIL = 1.0000 g
MASS OF ALUM FOIL (NET WEIGHT OF ALUM) = 0.6330 g
MASS OF EMPTY 50 mL BEAKER = 29.3380 g
MASS OF BEAKER + ALUM CRYSTALS = 39.8840 g
MASS OF ALUM (NET WEIGHT OF ALUM) = 10.5460 g

we added about 35 mL of de-ionized water and 12mL of 6M KOHsolution to the beaker. I converted the molarity to moles and got6M KOH (.012 L) = .072 mol KOH

When metallic aluminum comes into contact with aqueous solutions ofstrong bases like potassium hydroxide, KOH, it reacts to formhydrogen gas and a salt containing both aluminum and potassiumions.

2 Al (s) + 2 KOH (aq) + 6 H2O (l) ? 2 KAl(OH)4 (aq) + 3 H2(g)

This salt, KAl(OH)4, is soluble in solutions of strong acids, suchas sulfuric acid, H2 SO4, and reacts to form aluminum hydroxide,Al(OH)3, and potassium sulfate, K2 SO4.

2 KAl(OH)4 (aq) + H2 SO4 (aq) ? 2 Al(OH)3 (s) + K2 SO4 (aq) + 2 H2O(l)

Excess sulfuric acid is required to dissolve the Al(OH)3, and toform aluminum sulfate, Al2 (SO4)3.

2 Al(OH)3 (s) + 3 H2 SO4 (aq) ? Al2 (SO4)3 (aq) + 6 H2O (l)

As this solution is cooled, the aluminum and potassium sulfatesalts crystallize out of the solution as the alum. The equationbelow shows only the ions and the water involved in thecrystallization process.

K+ (aq) + Al3+ (aq) + 2 SO4 2- (aq) + 12 H2O (l) ? KAl(SO4)2 * 12H2O (s)

MY QUESTION IS.. I DONT KNOW WHICH EQUATION TO USE TO CALCULATE THEPERCENT YIELD. SHOULD IT BE THE FIRST ONE SINCE IT IS BEFORE ANY OFTHE PROCEDURE WAS DONE? BUT FROM THE FIRST EQUATION, IT DID NOTPRODUCE THE ALUM CRYSTALS YET : KAl(SO4)2 * 12H20

EQUATION FOR PERCENT YIELD:
100 % x [mass of actual yield / mass of theoretical yield]

Part A A fuel cell differs from a battery because the current is being generated from a reduction-oxidation (redox) reaction in which the reactant is consumed. A classic example of a fuel cell is the phosphoric acid fuel cell (PAFC), which have been used in stationary power generators, buses, and even submarines. Fuel cells require an electrolyte (similar to batteries) to carry electrically charged species between the electrodes, and a PAFC utilizes phosphoric acid (H3PO4) as its electrolyte. Phosphoric acid has three acidic protons that can dissociate in water, as highlighted in red here: H3PO4. However, it is considered a weak acid because some of the acid will remain in molecular form when dissolved in water. Write the complete ionic equation that depicts the dissociation of the first proton for the weak acid phosphoric acid (H3PO4). Make certain you include all charges for any ions produced. Express you answer as a chemical equation including phases. Titrations as analytical neutralization reactions Neutralization reactions can occur between any combination of weak/strong acids and bases. When we want to determine the concentration of a base in solution, we can apply the concept of neutralization by reacting the base with a known amount of an acid in the presence of an indicator (a compound that changes color depending on the pH). This method of determining the concentration of a base is called acid-base titration, and it can also be used to determine the concentration of an acid by titrating it with a known amount of base. A common acid to use for titrations is potassium hydrogen phthalate (written as KHP or KHPh; do not confuse the P for phosphorus). The reason KHP is common is because it is solid at room temperature, and we can accurately mass the amount that is added to solution. As a soluble salt, KHP completely dissociates to form a potassium ion (K+) and an acidic hydrogen phthalate ion (HP−), which is a weak acid that has only one acidic hydrogen. This ionization is depicted below. KHP(s) → K+(aq)+HP−(aq) Although ionization (the formation of ions) occurs as a result of acid dissociation for most weak acids, KHP ionizes before acid dissociation occurs. In other words, HP− is a weak acid ion. Part C If you wanted to determine how much KOH (potassium hydroxide; a strong base) was dissolved in water, you could titrate it with a known amount of KHP (potassium hydrogen phthalate; a weak acid) until a color change indicates that the base is completely neutralized. The molecular equation below depicts this neutralization reaction. KHP(aq)+KOH(aq)→K2P(aq)+H2O(l) Write the net ionic equation that depicts the neutralization of the base by potassium hydrogen phthalate. Instead of using the entire chemical formula of phthalate, use HP− to represent the acidic hydrogen phthalate ion and P2− to represent the phthalate ion. Express your answer as a net ionic equation including phases.

Balance the following Chemical Equations:

____Fe(s) + ____H2O(g) ® ____Fe3O4(s) + ____H2(g)

____C2H6(g) + ____O2(g) ® ____CO2(g) + ____H2O(g)

(C) ___ KClO3 (s) ® ___ KCl (s) + ___ O2 (g)

___ C6H14 (l) + ___ O2 (g) ® ___ CO2 (g) + ___ H2O (g)

___ C3H8O3 (l) + ___ O2 (g) ® ___ CO2 (g) + ___ H2O (l)

___ NaN3 (s) ® ___ Na (s) + ___ N2 (g)

__ C3H5N3O9 ® __ CO2 + ___ N2 + ___ H2O + ___ O2

Write and Balance the equations:

Aqueous calcium hydroxide reacts with aqueous sodium carbonate to produce solid calcium carbonate and aqueous sodium hydroxide.

Solid iron reacts with Oxygen gas to form solid Iron (II) oxide

Copper(II) sulfide is oxidized by molecular oxygen to produce gaseous sulfur trioxide and solid copper(II) oxide. The gaseous product then reacts with liquid water to produce liquid hydrogen sulfate as the only product. Write the two equations which represent these reactions.

Indicate what type, or types, of reaction each of the following represents: (precipitation, acid-base, and oxidation-reduction.)

(A) H2O(g) + C(s) ⟶ CO(g) +H2(g)

(B) 2KClO3(s) ⟶ 2KCl(s) +3O2(g)

(C) Al(OH)3(aq) +3HCl(aq) ⟶ AlCl3(aq) + 3H2O(l)

(D) Pb(NO3)2(aq) + H2SO4(aq) ⟶ PbSO4(s) + 2HNO3(aq)

4. Silver can be separated from gold because silver dissolves in nitric acid while gold does not. Is the dissolution of silver in nitric acid an acid-base reaction or an oxidation-reduction reaction? Explain your answer.

5. Determine the oxidation states of the elements in the compounds listed. None of the oxygen-containing compounds are peroxides or superoxides.

(A) H3PO4

(B) Al(OH)3

(C) SeO2

6. Complete and balance the following acid-base equations:

(A) A solution of HClO4 is added to a solution of LiOH.

(B) Aqueous H2SO4 reacts with NaOH.

7. Write the molecular, total ionic, and net ionic equations for the following reactions:

(A) Ca(OH)2(aq) + HC2H3O2(aq) ⟶

(B) H3PO4(aq) + CaCl2(aq) ⟶

8. Write the balanced equation, then calculate the number of moles and the mass of Mg required to react with 5.00 g of HCl and produce MgCl2 and H2. Ans: 1.67 g Mg

9. H2 is produced by the reaction of 118.5 mL of a 0.8775-M solution of H3PO4 according to the following equation: 2Cr + 2H3PO4 ⟶ 3H2 + 2CrPO4. How many grams of H2 are produced? Ans: .315 g H2

10. Automotive air bags inflate when a sample of sodium azide, NaN3, is very rapidly decomposed.

2NaN3(s) ⟶ 2Na(s) + 3N2(g)

What mass of sodium azide is required to produce 2.6 ft3 (73.6 L) of nitrogen gas with a density of 1.25 g/L?

Ans: 142 g NaN3

11. Urea, CO(NH2)2, is manufactured on a large scale for use in producing urea-formaldehyde plastics and as a fertilizer. What is the maximum mass of urea that can be manufactured from the CO2 produced by combustion of 1.00 x 104 grams of CO2?

CO2(g) + 2NH3(g) ⟶ CO(NH2)2(s) + H2O(l)

Ans: 1360 g urea

12. What volume o f 0.750 M hydrochloric acid solution can be prepared from the HCl produced by the reaction of 25.0 g of NaCl with excess sulfuric acid? NaCl(s) + H2SO4(l) ⟶ HCl(g) + NaHSO4(s)

Ans: .570 L

13. A sample of 0.53 g of carbon dioxide was obtained by heating 1.31 g of calcium carbonate. What is the percent yield for this reaction? CaCO3(s)⟶CaO(s) + CO2(s)

Ans: 92.0 %

14. Citric acid, C6H8O7, a component of jams, jellies, and fruity soft drinks, is prepared industrially via fermentation of sucrose by the mold Aspergillus niger. The equation representing this reaction is

C12H22O11 + H2O +3O2 ⟶2C6H8O 7+ 4H2O

What mass of citric acid is produced from the reaction of 150. grams of sucrose if the yield is 92.30%?

Ans: 155 g

15. The phosphorus pentoxide used to produce phosphoric acid for cola soft drinks is prepared by burning phosphorus in oxygen.

(A) What is the limiting reactant when 0.200 mol of P4 and 0.200 mol of O2 react according to P4+5O2 ⟶ P4O10?

(B) Calculate the percent yield if 10.0 g of P4O10 is isolated from the reaction.

Ans: 88.0 %

16. What is the limiting reactant when 1.50 g of lithium and 1.50 g of nitrogen combine to form lithium nitride, a component of advanced batteries, according to the following unbalanced equation? Li + N2 ⟶ Li3N

Ans: Li

17. What is the concentration of NaCl in a solution if titration of 15.00 mL of the solution with 0.2503 M AgNO3 requires 20.22 mL of the AgNO3 solution to reach the end point?

AgNO3(aq) + NaCl(aq) ⟶ AgCl(s) +NaNO (aq)

Ans: .3374 M

18. In a common medical laboratory determination of the concentration of free chloride ion in blood serum, a serum sample is titrated with a Hg(NO3)2 solution.

2Cl−(aq) + Hg(NO3)2(aq) ⟶ 2NO3−(aq) + HgCl2(s)

What is the Cl− concentration in a 0.25-mL sample of normal serum that requires 1.46 mL of .000825 M Hg(NO3)2(aq) to reach the end point?

Ans: 0.009636 M