Chemistry 8 Lesson 33: Preparation of hydrogen gas – Substitution reaction
1. Theoretical Summary
1.1. Modulation HYD2
a. In the laboratory
How to proceed?
– Materials are often used to make H2 in the laboratory are HCl acid and Zn metal.
– Put zinc tablets in HCl acid solution
Video 1: H gas modulation reaction2 from the reaction of Zn and Acid HCl
Phenomenon – Explanation
+ When the zinc tablet is put into HCl acid solution → the solution boils and gas is released, the zinc tablet gradually dissolves.
+ After the reaction is over, take 1-2 drops of the solution in the test tube and evaporate it → a white solid is obtained.
Explain: Chemical equation: Zn + 2HCl → ZnCl2 + FRIENDS2
– To modulate THEM2 In the laboratory one can replace HCl solution with H2SO4 dilute and replace Zn with Fe, Al, …
– The test tube just conducted the experiment heats up a lot, showing that the reaction that occurs is an exothermic reaction.
– HYDRAULIC2 Less soluble in water and lighter than air, we can collect H2 in two ways: push water and push air.
– When collecting O2 By pushing the air, care must be taken so that the mouth of the flask is facing up, because O2 heavier than air.
⇒ So when collecting2 By pushing air we have to point the mouth of the test tube downwards because the gas H2 lighter than air.
b. In industry
Video 2: Electrolysis of water experiment to prepare Oxygen, Hydrogen
– People manipulate THEM2 by electrolysis of water or using deoxidized coal of H2O in coal gas furnace or H preparation2 from natural gas, petroleum gas
1.2. What is the reaction?
A substitution reaction is a chemical reaction between an element and a compound in which an atom of a single element replaces an atom of another element in a compound.
2. Illustrated exercise
2.1. Type 1: Classification of reactions
Lesson 1: Which of the following reactions is a substitution reaction? Please explain that choice?
a. 2Mg + O2 → 2MgO
b. KMnO4 → CZK2MnO4+MnO2+O2
c. Fe + CuCl2 → FeCl2 + Cu
d. Mg(OH)2 → MgO + HO2O
e. Fe2O3 + FRIENDS2 → Fe + H2O
f. Cu + AgNO3 → Ag + Cu(NO3)2
The reaction is thus: c ; e ; g because atoms of the element (Fe , H2 , Cu) has replaced the atom of 1 element in the compound (CuCl2 ; Fe2O3 ; AgNO3).
2.2. Form 2: Hydrogen modulation method
When collecting oxygen gas into a test tube by blowing air, how should the test tube be positioned? Why? For hydrogen gas, is it possible? Why?
Because O . gas2 (M = 32) is heavier than air (M = 29), so when collecting oxygen, we can tilt the test tube or stand, while H2 lighter than air, so when collecting H2 The test tube must be inverted, the test tube must not be left standing.
2.3. Form 3: Determination of the volume of Hydrogen gas
Lesson 1: React 22.4g of iron with a dilute solution containing 24.5g of sulfuric acid.
a) Which substance is left over after the reaction and how many grams are left over?
b) Calculate the volume of hydrogen gas collected at dktc.
nFe = 22.4 / 56 = 0.4 mol
nH2SO4 = 24.5 / 98 = 0.25 mol
a) The chemical equation for the reaction
Fe + H2SO4 → FeSO4 + FRIENDS2
1 mol 1 mol
Compare the ratio: (0.4/1) > (0.25/1) → residual Fe mass.
mFe residual: (0.4 – 0.25.56 = 8.4g.
b) According to the above reaction equation:
Due to the excess Fe mass, calculate the volume of gas H2 in moles of H2SO4
DRAWH2 = 0.25.22.4 = 5.6 liters.
3.1. Essay exercises
Question 1: For 6.5g Zn react with hydrochloric acid to see gas rising with a volume of?
Verse 2: Put an iron rod weighing 5.53g into a flask containing a solution of hydrochloric acid solution to obtain solution A and the gas rises. Evaporate solution A to get m(g) of solid. Ask what is solution A and find m?
Question 3: Calculating the initial mass of Al when reacting with sulfuric acid shows that 1.68(l) gas is released.
Question 4: Completely electrolyze 2 liters of water in the liquid state (knowing the density D of water is 1 kg/liter), the volume of hydrogen gas and the volume of oxygen gas obtained (at ktc) respectively?
Question 5: People add zinc or iron to react with hydrochloric acid HCl solution to prepare hydrogen gas. If you want to prepare 2.24 liters of hydrogen gas (dktc), how many grams of zinc or iron must be used, respectively?
3.2. Multiple choice exercises
Question 1: Choose the correct answer:
A. The reaction between Fe and HCl is an OXH-Reduction reaction
B. A substitution reaction is a reaction between a compound and a compound
C. CaCO3 −to→ CaO + CO2 is a reduction reaction
D. HO2 heavier than air
Verse 2: Let Al work on H2SO4 dilute to produce some products
Question 3: Hydrogen modulation in industry, people use:
A. Give Zn + HCl
B. Fe + HIM2SO4
C. Water electrolysis
D. Kerosene gas
Question 4: After the reaction of Zn and HCl in the laboratory, put a burning lightstick into the gas pipe, the released gas can burn in the air with what color flame?
B. Light green
Question 5: Choose the wrong answer:
A. Laboratory metals react with HCl or H2SO4 dilute is Na
B. Hydrogen is sparingly soluble in water
D. Fe + 2HCl → FeCl2 + FRIENDS2
After the lesson to know:
- How to modulate THEY2 in the laboratory and in industry
- The concept of such reaction.