Chemistry 9 Lesson 3: Chemical properties of acids

1. Theoretical Summary

1.1. Chemical properties

• Acids discolor the color indicator

Acid solution turns blue litmus red.

• Acids react with metals:

Fe + 2HCl → FeCl₂ + FRIENDS₂

Fe + H₂SO₄ → FeSO₄ + FRIENDS₂

Acid solutions react with some metals to form salts and release H . gas₂ (except Cu, Ag, Au)

HNO solution₃, H₂SO₄ It reacts with many metals but does not release H .₂

• Acid reacts with base

Acids react with bases to form salts and water

Cu(OH)₂ + FRIENDS₂SO₄ → CuSO₄ + 2 HOUSES₂O

• Acids react with basic oxides

Acids react with basic oxides to form salts and water.

Fe₂O₃ + 6HCl → 2FeCl₂ + 3 HOURS₂O

1.2. Strong acid, weak acid

2. Illustrated example

2.1. Form 1: Write a chemical equation for the properties of acids

There are the following substances: CuO, Mg, Al₂O₃, Fe(OH)₃, Fe₂O₃. Choose one of the given substances that react with HCl solution to produce:

a) The gas is lighter than air and flammable in air.

b) The solution is blue.

c) The solution is yellow-brown.

d) The solution is colorless.

Write the chemical equations.

Solution guide

a. A gas that is lighter than air and flammable in air is H₂.

Chemical equation:

Mg + 2HCl → MgCl₂ + FRIENDS₂↑

b. The blue color solution is CuCl . solution₂.

Chemical equation:

CuO + 2HCl → CuCl₂ + FRIENDS₂O

c. The yellow-brown solution is FeCl . solution₃.

Chemical equation:

Fe(OH)₃ + 3HCl → FeCl₃ + 3 HOURS₂O

Or Fe₂O₃ + 6HCl → 2FeCl₃ + 3 HOURS₂O

d. Colorless solutions are MgCl . solutions₂, AlCl₃.

Chemical equation:

Al₂O₃ + 6HCl → 2AlCl₃ + 3 HOURS₂O

Mg + 2HCl → MgCl₂ + FRIENDS₂↑

2.2. Form 2: Determine the formula of chemistry

Question 1: Give 32g of a trivalent metal oxide completely dissolved in 294g of H . solution₂SO₄. Find the formula for the metal oxide above.

Solution guide

The formula to find has the form: X₂O₃

– Volume H₂SO₄: m = 20.294100 = 58.8 g

– Number of moles H₂SO₄ = 0.6 mol.

– Reaction Equation:

X₂O₃ + 3 HOURS₂SO₄ → X₂(SO)₄)₃ + 3 HOURS₂O

0.2 mol 0.6mol

Molecular mass of oxide: M = 160.

So that oxide is Fe₂O₃.

Verse 2: Find the chemical formula of an acid with the following mass composition:

H: 2.1%; N: 29.8%; O: 68.1%.

Solution guide

Let the chemical formula of the acid be H_xWOMEN_yO_z. We have:

x : y : z = 2.1 : 2.1 : 4.2 = 1 : 1 : 2

→ The chemical formula of the acid is HNO₂ (nitrous acid).

2.3. Form 3: Exercises about salt carbonates and hydrocarbons reacting with acids

a. Slowly add solution X containing x moles of HCl to solution Y containing y moles of Na .₂HAVE₃ (x < 2y), then a solution of Z containing V liters of gas is obtained. Calculate V?

b. If solution Y is added to solution X, solutions A and V . are obtained_first liters of gas. The reactions are complete and the gas volume is measured at standard conditions. Find the relationship between VU_first with x, y.

Solution guide

a. Slowly add HCl to Na₂HAVE₃, the reaction takes place as follows:

HCl + Na₂HAVE₃ → NaHCO₃ + NaCl (1)

But according to the beginning of the article, there is gas coming out, so the reaction continues:

HCl + NaHCO₃ → NaCl + CO₂ + FRIENDS₂O (2)

Reaction (1) will proceed completely, yielding y moles of NaHCO₃.

For reaction (2) to occur, then x > y.

Since the problem gives x < 2y, (2) react according to the number of moles of HCl remaining.

So V = 22.4.(x – y)

b. When giving Na₂HAVE₃ into HCl:

Na₂HAVE₃ + 2HCl → 2NaCl + CO₂ + FRIENDS₂O

1 mol 2 mol

y mol x mol

The problem gives x < 2y, so we calculate the number of moles of gas produced according to HCl:

DRAW_first = x / 2 . 22.4

3. Practice

3.1. Essay exercises

Question 1: There are the following oxides: Fe₂O₃, SO₂, CuO, MgO, CO₂.

a) Which oxides react with H . solution?₂SO₄?

b) Which oxides react with NaOH solution?

c) Which oxides can react with H .?₂O?

Write chemical equations.

Verse 2: Find the chemical formulas of acids with the following mass composition:

a) H: 2.4%; S : 39.1%; O: 58.5%.

b) H: 3.7%; P: 37.8%; O: 58.5%.

Question 3: Solution X contains a mole of HCl, solution Y contains b mole of Na .₂HAVE₃ (a < 2b)
a) If X is added very slowly to Y, then V . is obtained_first liters of gas.
b) Put Y in X, get V₂ liters of gas.
Formula for calculating V_first, VOICE₂ according to a, b

3.2. Multiple choice exercises

Question 1: H solution₂SO₄ Which substance reacts to produce hydrogen gas?

A. NaOH

B. Fe

C. CaO

D. CO₂

Verse 2: Which chemical property is not an acid?

A. React with metal

B. Effect with salt

C. React with acid oxide

D. React with basic oxides

Question 3: The solution reacts with CuO to give a product that is a blue solution:

A. NaOH . solution

B. Na . solution₂HAVE₃

C. HCl solution

D. Ca(OH) solution₂

Question 4: A series of metals that react with H . solutions₂SO₄ dilution is:

A. Fe, Cu, Mg

B. Zn, Fe, Cu

C. Zn, Fe, Al.

D. Fe, Zn, Ag

Question 5: The group of substances that react with water and with HCl solution are:

A. Na₂O, SO₃ , HAVE₂

B. KY₂O, P₂O₅, High

C. Bao, SO₃, P₂O₅

D. CaO, BaO, Na₂O

4. Conclusion

The content of the lesson is summarized as follows: