Strong oxides. Chemical properties of water

Oxides.

These are complex substances consisting of TWO elements, one of which is oxygen. For example:

CuO – copper(II) oxide

AI 2 O 3 – aluminum oxide

SO 3 – sulfur oxide (VI)

Oxides are divided (classified) into 4 groups:

Na 2 O– Sodium oxide

CaO – Calcium Oxide

Fe 2 O 3 – iron (III) oxide

2). Acidic– These are oxides non-metals. And sometimes metals if the oxidation state of the metal is > 4. For example:

CO 2 – Carbon monoxide (IV)

P 2 O 5 – Phosphorus (V) oxide

SO 3 – Sulfur oxide (VI)

3). Amphoteric– These are oxides that have the properties of both basic and acidic oxides. You need to know the five most common amphoteric oxides:

BeO–beryllium oxide

ZnO–zinc oxide

AI 2 O 3 – Aluminum oxide

Cr 2 O 3 – Chromium (III) oxide

Fe 2 O 3 – Iron (III) oxide

4). Non-salt-forming (indifferent)– These are oxides that do not exhibit the properties of either basic or acidic oxides. There are three oxides to remember:

CO – carbon monoxide (II) carbon monoxide

NO – nitric oxide (II)

N 2 O – nitric oxide (I) laughing gas, nitrous oxide

Methods for producing oxides.

1). Combustion, i.e. interaction with oxygen of a simple substance:

4Na + O 2 = 2Na 2 O

4P + 5O 2 = 2P 2 O 5

2). Combustion, i.e. interaction with oxygen of a complex substance (consisting of two elements) thus forming two oxides.

2ZnS + 3O 2 = 2ZnO + 2SO 2

4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2

3). Decomposition three weak acids. Others do not decompose. In this case, acid oxide and water are formed.

H 2 CO 3 = H 2 O + CO 2

H 2 SO 3 = H 2 O + SO 2

H 2 SiO 3 = H 2 O + SiO 2

4). Decomposition insoluble grounds. A basic oxide and water are formed.

Mg(OH) 2 = MgO + H 2 O

2Al(OH) 3 = Al 2 O 3 + 3H 2 O

5). Decomposition insoluble salts A basic oxide and an acidic oxide are formed.

CaCO 3 = CaO + CO 2

MgSO 3 = MgO + SO 2

Chemical properties.

I. Basic oxides.

alkali.

Na 2 O + H 2 O = 2NaOH

CaO + H 2 O = Ca(OH) 2

СuO + H 2 O = the reaction does not occur, because possible base containing copper - insoluble

2). Interaction with acids, resulting in the formation of salt and water. (Base oxide and acids ALWAYS react)

K 2 O + 2HCI = 2KCl + H 2 O

CaO + 2HNO 3 = Ca(NO 3) 2 + H 2 O

3). Interaction with acidic oxides, resulting in the formation of salt.

Li 2 O + CO 2 = Li 2 CO 3

3MgO + P 2 O 5 = Mg 3 (PO 4) 2

4). Interaction with hydrogen produces metal and water.

CuO + H 2 = Cu + H 2 O

Fe 2 O 3 + 3H 2 = 2Fe + 3H 2 O

II.Acidic oxides.

1). Interaction with water should form acid.(OnlySiO 2 does not interact with water)

CO 2 + H 2 O = H 2 CO 3

P 2 O 5 + 3H 2 O = 2H 3 PO 4

2). Interaction with soluble bases (alkalis). This produces salt and water.

SO 3 + 2KOH = K 2 SO 4 + H 2 O

N 2 O 5 + 2KOH = 2KNO 3 + H 2 O

3). Interaction with basic oxides. In this case, only salt is formed.

N 2 O 5 + K 2 O = 2KNO 3

Al 2 O 3 + 3SO 3 = Al 2 (SO 4) 3

Basic exercises.

1). Complete the reaction equation. Determine its type.

K 2 O + P 2 O 5 =

Solution.

To write down what is formed as a result, it is necessary to determine what substances have reacted - here it is potassium oxide (basic) and phosphorus oxide (acidic) according to the properties - the result should be SALT (see property No. 3) and salt consists of atoms metals (in our case potassium) and an acidic residue which includes phosphorus (i.e. PO 4 -3 - phosphate) Therefore

3K 2 O + P 2 O 5 = 2K 3 RO 4

type of reaction - compound (since two substances react, but one is formed)

2). Carry out transformations (chain).

Ca → CaO → Ca(OH) 2 → CaCO 3 → CaO

Solution

To complete this exercise, you must remember that each arrow is one equation (one chemical reaction). Let's number each arrow. Therefore, it is necessary to write down 4 equations. The substance written to the left of the arrow (starting substance) reacts, and the substance written to the right is formed as a result of the reaction (reaction product). Let's decipher the first part of the recording:

Ca + …..→ CaO We note that a simple substance reacts and an oxide is formed. Knowing the methods for producing oxides (No. 1), we come to the conclusion that in this reaction it is necessary to add -oxygen (O 2)

2Ca + O 2 → 2CaO

Let's move on to transformation No. 2

CaO → Ca(OH) 2

CaO + ……→ Ca(OH) 2

We come to the conclusion that here it is necessary to apply the property of basic oxides - interaction with water, because only in this case a base is formed from the oxide.

CaO + H 2 O → Ca(OH) 2

Let's move on to transformation No. 3

Ca(OH) 2 → CaCO 3

Ca(OH) 2 + ….. = CaCO 3 + …….

We come to the conclusion that here we are talking about carbon dioxide CO 2 because only when interacting with alkalis it forms a salt (see property No. 2 of acid oxides)

Ca(OH) 2 + CO 2 = CaCO 3 + H 2 O

Let's move on to transformation No. 4

CaCO 3 → CaO

CaCO 3 = ….. CaO + ……

We come to the conclusion that more CO 2 is formed here, because CaCO 3 is an insoluble salt and it is during the decomposition of such substances that oxides are formed.

CaCO 3 = CaO + CO 2

3). Which of the following substances does CO 2 interact with? Write the reaction equations.

A). Hydrochloric acid B). Sodium hydroxide B). Potassium oxide d). Water

D). Hydrogen E). Sulfur(IV) oxide.

We determine that CO 2 is an acidic oxide. And acidic oxides react with water, alkalis and basic oxides... Therefore, from the given list we select answers B, C, D And it is with them that we write down the reaction equations:

1). CO 2 + 2NaOH = Na 2 CO 3 + H 2 O

2). CO 2 + K 2 O = K 2 CO 3

Interaction of water with metals.

If calcium shavings are placed in a cylinder of water, gas bubbles will begin to break away from the surface of the calcium, just like from the surface of zinc placed in a solution of sulfuric acid. When we bring a lit splinter to the hole in the cylinder, we will observe flashes. This is hydrogen burning. The water in the cylinder becomes cloudy. The white suspended particles that appear in the cylinder are calcium hydroxide Ca(OH)2. The ongoing reaction is expressed by the equation:

Ca + 2H 2 0 = 2Ca (OH) 2 + H 2

During this reaction, from a water molecule H 2 O, which can be represented as H-OH (group - OH - hydroxo group), -OH is converted into calcium hydroxide. Since the calcium atom is divalent, it displaces two hydrogen atoms from two water molecules, and the remaining two -OH groups combine with the calcium atom.

The reaction of sodium with water proceeds even more vigorously. Place a piece of sodium in a glass of water. Sodium floats to its surface, melts, turning into a shiny drop. It moves quickly along the surface of the water, emitting hissing and decreasing in size. Having evaporated the solution, we will find a white solid substance - sodium hydroxide NaOH

2Na + 2НН = 2NaOH + H 2

Sodium and calcium are among the most chemically active.

Interaction of water with non-metal oxides .

Let's burn red phosphorus in a jar on a spoon. Let's add a little water and wait until the resulting phosphorus oxide (V) P 2 0 5 dissolves. Add a few drops of purple litmus to the solution. The litmus will turn red. This means that the solution contains an acid. Phosphorus oxide (V) combines with water, and phosphoric acid H 3 P0 4 is obtained:

Р 2 0 5 + ЗН 2 0 = 2Н 3 Р0 4

Let's burn sulfur in a jar with some water in it and examine the resulting solution with litmus solution. It will also turn red. Sulfur oxide (IV) S0 2, formed during the combustion of sulfur, combined with water, and sulfurous acid was obtained:

S0 2 + H 2 0 = H 2 S0 2

Sulfur oxide (VI), interacting with water, forms sulfuric acid H 2 S0 4:

SO 2+ H 2 O = H 2 S0 4

Nitrogen can form oxide N205, which reacts with water to form nitric acid:

N 2 0 5 + N 2 0 = 2HN0 3

Compounds of non-metal oxides with water are classified as acids.

Interaction of water with metal oxides.

Let us now consider the relationship of metal oxides to water. Pour copper oxide CuO, iron oxide Fe203, zinc oxide ZnO and calcium oxide CaO into cups and add a little water to each. Oxides of copper, iron and zinc do not dissolve in water and do not combine with it. Calcium oxide, or quicklime, behaves differently.

When pouring water over pieces of quicklime, such strong heating is observed that part of the water turns into steam, and pieces of quicklime, crumbling, turn into dry, loose powder - slaked lime, or calcium hydroxideCa(OH) 2:

CaO + H 2 0 = Ca(OH) 2

Like calcium oxide, sodium and potassium oxides combine with water:

Na 2 0 + H 2 0 = 2NaOH

K 2 0+N 2 0 = 2KON

These reactions produce sodium hydroxide NaOH and potassium hydroxide KOH.

Thus, some metal oxides do not react with water (the majority of them), while others (potassium oxide, sodium oxide, calcium oxide, barium oxide, etc.) combine with it, forming hydroxides, which are classified as bases.

(Inorganic chemistry grade 7-8 author Yu. V. Khodakov and others)

Chemical properties of acid oxides

1. Acidic oxides react with basic oxides and bases to form salts.

In this case, the rule applies - at least one of the oxides must correspond to a strong hydroxide (acid or alkali).

Acidic oxides of strong and soluble acids interact with any basic oxides and bases:

SO 3 + CuO = CuSO 4

SO 3 + Cu(OH) 2 = CuSO 4 + H 2 O

SO 3 + 2NaOH = Na 2 SO 4 + H 2 O

SO 3 + Na 2 O = Na 2 SO 4

Acidic oxides of water-insoluble and unstable or volatile acids react only with strong bases (alkalis) and their oxides. In this case, the formation of acidic and basic salts is possible, depending on the ratio and composition of the reagents.

For example , sodium oxide interacts with carbon monoxide (IV), and copper oxide (II), which corresponds to the insoluble base Cu(OH) 2, practically does not interact with carbon monoxide (IV):

Na 2 O + CO 2 = Na 2 CO 3

CuO + CO 2 ≠

2. Acidic oxides react with water to form acids.

Exception — silicon oxide, which corresponds to insoluble silicic acid. Oxides, which correspond to unstable acids, usually react with water reversibly and to a very small extent.

SO 3 + H 2 O = H 2 SO 4

3. Acidic oxides react with amphoteric oxides and hydroxides to form salt or salt and water.

Please note that, as a rule, only oxides of strong or moderate acids react with amphoteric oxides and hydroxides!

For example , sulfuric acid anhydride (sulfur oxide (VI)) reacts with aluminum oxide and aluminum hydroxide to form a salt - aluminum sulfate:

3SO 3 + Al 2 O 3 = Al 2 (SO 4) 3

3SO 3 + 2Al(OH) 3 = Al 2 (SO 4) 3 + 3H 2 O

But carbon monoxide (IV), which corresponds to weak carbonic acid, no longer interacts with aluminum oxide and aluminum hydroxide:

CO 2 + Al 2 O 3 ≠

CO 2 + Al(OH) 3 ≠

4. Acidic oxides interact with salts of volatile acids.

The following rule applies: in the melt, less volatile acids and their oxides displace more volatile acids and their oxides from their salts.

For example , solid silicon oxide SiO 2 will displace the more volatile carbon dioxide from calcium carbonate when fused:

CaCO 3 + SiO 2 = CaSiO 3 + CO 2

5. Acidic oxides are capable of exhibiting oxidizing properties.

Usually, oxides of elements in the highest oxidation state - typical (SO 3, N 2 O 5, CrO 3, etc.). Some elements with an intermediate oxidation state (NO 2, etc.) also exhibit strong oxidizing properties.

6. Restorative properties.

Reductive properties, as a rule, are exhibited by oxides of elements in intermediate oxidation states(CO, NO, SO 2, etc.). In this case, they are oxidized to the highest or closest stable oxidation state.

For example , sulfur oxide (IV) is oxidized by oxygen to sulfur oxide (VI):

2SO2 + O2 = 2SO3

Oxides are complex substances consisting of two chemical elements, one of which is oxygen with an oxidation state ($-2$).

The general formula of oxides is: $E_(m)O_n$, where $m$ is the number of atoms of the element $E$, and $n$ is the number of oxygen atoms. Oxides can be hard(sand $SiO_2$, varieties of quartz), liquid(hydrogen oxide $H_2O$), gaseous(carbon oxides: carbon dioxide $CO_2$ and carbon dioxide $CO$ gases). Based on their chemical properties, oxides are divided into salt-forming and non-salt-forming.

Non-salt-forming These are oxides that do not react with alkalis or acids and do not form salts. There are few of them, they contain non-metals.

Salt-forming These are oxides that react with acids or bases to form salt and water.

Among the salt-forming oxides there are oxides basic, acidic, amphoteric.

Basic oxides- these are oxides that correspond to bases. For example: $CaO$ corresponds to $Ca(OH)_2, Na_2O to NaOH$.

Typical reactions of basic oxides:

1. Basic oxide + acid → salt + water (exchange reaction):

$CaO+2HNO_3=Ca(NO_3)_2+H_2O$.

2. Basic oxide + acidic oxide → salt (compound reaction):

$MgO+SiO_2(→)↖(t)MgSiO_3$.

3. Basic oxide + water → alkali (compound reaction):

$K_2O+H_2O=2KOH$.

Acidic oxides- these are oxides that correspond to acids. These are non-metal oxides:

N2O5 corresponds to $HNO_3, SO_3 - H_2SO_4, CO_2 - H_2CO_3, P_2O_5 - H_3PO_4$, as well as metal oxides with high oxidation states: $(Cr)↖(+6)O_3$ corresponds to $H_2CrO_4, (Mn_2)↖(+7 )O_7 — HMnO_4$.

Typical acid oxide reactions:

1. Acid oxide + base → salt + water (exchange reaction):

$SO_2+2NaOH=Na_2SO_3+H_2O$.

2. Acidic oxide + basic oxide → salt (compound reaction):

$CaO+CO_2=CaCO_3$.

3. Acid oxide + water → acid (compound reaction):

$N_2O_5+H_2O=2HNO_3$.

This reaction is possible only if the acid oxide is soluble in water.

Amphoteric are called oxides, which, depending on conditions, exhibit basic or acidic properties. These are $ZnO, Al_2O_3, Cr_2O_3, V_2O_5$. Amphoteric oxides do not directly combine with water.

Typical reactions of amphoteric oxides:

1. Amphoteric oxide + acid → salt + water (exchange reaction):

$ZnO+2HCl=ZnCl_2+H_2O$.

2. Amphoteric oxide + base → salt + water or complex compound:

$Al_2O_3+2NaOH+3H_2O(=2Na,)↙(\text"sodium tetrahydroxoaluminate")$

$Al_2O_3+2NaOH=(2NaAlO_2)↙(\text"sodium aluminate")+H_2O$.

Oxides are called complex substances whose molecules include oxygen atoms in oxidation state - 2 and some other element.

can be obtained through the direct interaction of oxygen with another element, or indirectly (for example, during the decomposition of salts, bases, acids). Under normal conditions, oxides come in solid, liquid and gaseous states; this type of compound is very common in nature. Oxides are found in the Earth's crust. Rust, sand, water, carbon dioxide are oxides.

They are either salt-forming or non-salt-forming.

Salt-forming oxides- These are oxides that form salts as a result of chemical reactions. These are oxides of metals and non-metals, which, when interacting with water, form the corresponding acids, and when interacting with bases, the corresponding acidic and normal salts. For example, Copper oxide (CuO) is a salt-forming oxide, because, for example, when it reacts with hydrochloric acid (HCl), a salt is formed:

CuO + 2HCl → CuCl 2 + H 2 O.

As a result of chemical reactions, other salts can be obtained:

CuO + SO 3 → CuSO 4.

Non-salt-forming oxides These are oxides that do not form salts. Examples include CO, N 2 O, NO.

Salt-forming oxides, in turn, are of 3 types: basic (from the word « base » ), acidic and amphoteric.

Basic oxides These metal oxides are called those that correspond to hydroxides belonging to the class of bases. Basic oxides include, for example, Na 2 O, K 2 O, MgO, CaO, etc.

Chemical properties of basic oxides

1. Water-soluble basic oxides react with water to form bases:

Na 2 O + H 2 O → 2NaOH.

2. React with acid oxides, forming the corresponding salts

Na 2 O + SO 3 → Na 2 SO 4.

3. React with acids to form salt and water:

CuO + H 2 SO 4 → CuSO 4 + H 2 O.

4. React with amphoteric oxides:

Li 2 O + Al 2 O 3 → 2LiAlO 2.

If the composition of the oxides contains a non-metal or a metal exhibiting the highest valence (usually from IV to VII) as the second element, then such oxides will be acidic. Acidic oxides (acid anhydrides) are those oxides that correspond to hydroxides belonging to the class of acids. These are, for example, CO 2, SO 3, P 2 O 5, N 2 O 3, Cl 2 O 5, Mn 2 O 7, etc. Acidic oxides dissolve in water and alkalis, forming salt and water.

Chemical properties of acid oxides

1. React with water to form an acid:

SO 3 + H 2 O → H 2 SO 4.

But not all acidic oxides react directly with water (SiO 2, etc.).

2. React with based oxides to form a salt:

CO 2 + CaO → CaCO 3

3. React with alkalis, forming salt and water:

CO 2 + Ba(OH) 2 → BaCO 3 + H 2 O.

Part amphoteric oxide includes an element that has amphoteric properties. Amphotericity refers to the ability of compounds to exhibit acidic and basic properties depending on conditions. For example, zinc oxide ZnO can be either a base or an acid (Zn(OH) 2 and H 2 ZnO 2). Amphotericity is expressed in the fact that, depending on the conditions, amphoteric oxides exhibit either basic or acidic properties.

Chemical properties of amphoteric oxides

1. React with acids to form salt and water:

ZnO + 2HCl → ZnCl 2 + H 2 O.

2. React with solid alkalis (during fusion), forming as a result of the reaction salt - sodium zincate and water:

ZnO + 2NaOH → Na 2 ZnO 2 + H 2 O.

When zinc oxide interacts with an alkali solution (the same NaOH), another reaction occurs:

ZnO + 2 NaOH + H 2 O => Na 2.

Coordination number is a characteristic that determines the number of nearby particles: atoms or ions in a molecule or crystal. Each amphoteric metal has its own coordination number. For Be and Zn it is 4; For and Al it is 4 or 6; For and Cr it is 6 or (very rarely) 4;

Amphoteric oxides are usually insoluble in water and do not react with it.

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