You will need

- is the molar mass;
- - the valence;
- - acidity;
- - basicity.

Instruction

1

**The equivalent**probability weight is one of the most important characteristics of substances. When solving problems it is denoted as M EQ. Is determined by the molar equivalent weight of any compound, the chemical formula of the studied

**substances**and its belonging to a particular class of chemical compounds.

2

In order to find the molar mass equivalents, you'll need to know such factors as molar mass – the mass of one mole

**of a substance**. The basicity of acids the number of hydrogen atoms that the acid can attach. The acidity of the base is determined by the number of OH-ions. Valence – the number of chemical bonds that an atom forms with other elements in the mix.3

The formula for finding the equivalent mass

**of a substance**depends on what class applies the test compound. For example, for finding the equivalent**substances**of the oxides, you will need to divide molar mass of compound by the number of oxygen atoms, is pre-multiplied by two. For example, for Fe2O3 equivalent weight is equal to 56*2 + 16*3/3*2 = 26,7 g/mol.4

To find the molar mass of the equivalent

**substances**at the base, divide the molar mass of the base in its acidity. So, for the base Ca(OH)2 equivalent will be equal to 40 + (16+2)*2/2 = 37 g/mol.5

To find equivalent

**substances**for the acid, you will need to do the following: divide the molar mass of the acid is its basicity. To find the molar mass of equivalent**of the substance**sulfuric acid, H2SO4 divide 1*2 + 32 + 16*4/2 = 49 g/mol.6

Finally, to find equivalent

**substances**of salt, divide the molar mass**of the substance**by the number of metal atoms, multiplied by its valence. For example, the molar mass equivalent**substances**salts Al2(SO4)3 = 27*2 + (32 + 16*4)*3/1*2 = 171 g/mol.# Advice 2 : How to find the equivalent mass of

The chemical elements are connected to each other in strictly defined proportions. That is why there was such a thing as equivalent and equivalent weight. ("Equivalent" literally means "equal", "equivalent"). What is the equivalent in the chemical sense of the word? How to calculate the equivalent (or equivalent

**mass**?Instruction

1

Equivalents and equivalent mass are usually determined either according to the analysis of compounds or on the basis of the results of the substitution of one element with another. It is easy to understand that to determine equivalent (or equivalent mass) of an element does not necessarily come from its compounds with hydrogen. The equivalent (equivalent mass) can similarly compute the compound of this element with any other, equivalent (equivalent mass) is known.

2

Example. When connecting 1.50 grams of sodium with excess chlorine formed 3.81 grams of sodium chloride. You need to find the equivalent mass of sodium and its equivalent, if it is known that the equivalent weight of chlorine is equal to 35,45 g/mol.Solution. Subtract from the total mass of the formed product of the original mass of sodium.

Thus, 3, 81 – 1, 50 = 2, 31

Thus, 3, 81 – 1, 50 = 2, 31

3

That is, in the formed product (in your case sodium chloride) 1.50 grams of sodium accounts for 2.31 grams of chlorine. From this it follows that knowing the equivalent weight of chlorine (35, 45 gram/mol), you can easily find the equivalent mass of sodium by the following formula:

35, 45 x 1, 50 / 2, 31 is the Equivalent mass of sodium is equal to 23,0 g/mol.

35, 45 x 1, 50 / 2, 31 is the Equivalent mass of sodium is equal to 23,0 g/mol.

4

Molar mass of sodium will also be equal to 23,0 g/mol. From this it follows that the equivalent of sodium is equal to one pray (as the molar equivalent weight of sodium is the same).

5

The concept of equivalents and equivalent masses also apply to complex substances. The equivalent complex substance called this number that communicates without residue with one equivalent of hydrogen.

Useful advice

Currently under the equivalent item made to understand this quantity, which is connected with one mole of hydrogen atoms or replaces the same number of hydrogen atoms in chemical reactions. The mass of one equivalent of an element is called its equivalent weight.

# Advice 3 : How to determine the factor of equivalence

Chemical equivalent is a particle of matter that takes (gives) one of the hydrogen-ion or hydroxyl ion, takes (gives) one electron in redox reactions and react with one hydrogen atom or one equivalent of another substance. A number that indicates which part of the molecules of a substance corresponds to its equivalent is called the

**factor****of equivalence**, which can be either equal to one or less.Instruction

1

Consider, for example, reaction of sodium hydroxide with phosphoric acid. Depending on which ratio was taken as starting material, can produce different products. NaOH + H3PO4 = NaH2PO4 + H2O2NaOH + H3PO4 = Na2HPO4 + 2H2O3NaOH + H3PO4 = Na3PO4 + 3H2O

2

In the first case, for each molecule of alkali that reacts, one molecule of the acid. Therefore, the factor

**of equivalence**of sodium hydroxide equal to 1, and the factor**of equivalence of**acid and equal to 1.3

In the second case, one molecule of acid reacts with two molecules of alkali. That is, one molecule of sodium hydroxide has a 1/2 molecule of the acid. Therefore, the factor

**of equivalence**of alkali is still equal to 1, and the factor**of equivalence**of the acid is now equal to 1/2.4

Accordingly, in the third case, the factor

**of equivalence**of sodium hydroxide is 1 and the acid - 1/3, since one molecule of alkali there are three molecules of acid.5

For different classes of chemical compounds exist appropriate formula for the calculation of the factor

**of equivalence**. For example, for an item, it is calculated as: 1/V, where V – valence of the element in a particular compound. For example, the main oxide of chromium – Cr2O3. In this compound chromium has a valence equal to 3. Hence its Fe (factor**equivalence**) is equal to 1/3. But if you consider potassium bichromate (potassium dichromate) with the formula K2Cr2O7, there is the valence of chromium is 6, hence its PV will be 1/6.6

If we are talking about a simple substance, that is, such whose molecules consist of atoms of only one element, the factor

**of equivalence**calculated by the formula 1/ВхN, where the valence of the element, and N is the number of atoms in the molecule. It is easy to see that, for example, oxygen and ozone, though their composition is only one element will have a different PV. Oxygen having the formula O2 molecule, it will be equal to 1/4, and ozone with the formula O3, respectively, 1/6.# Advice 4 : How to calculate equivalent weight of the oxide and metal

Equivalent that amount of a chemical element, which either binds or replaces one mole of hydrogen atoms. Accordingly, the mass of one equivalent is called the equivalent mass (Me), and is expressed in g/mol. To students in chemistry often aim to determine the equivalent mass of a substance (compound). For example,

**metal**and formed them**oxide**.Instruction

1

First and foremost, you should remember a few simple rules. If we are talking about the metal, its equivalent mass is calculated by the formula: Me=M/V, where M is the atomic mass

**of the metal**, and In his valence. Consider this rule with specific examples.2

Calcium (CA). Its atomic weight 40,08. Rounded take it over 40. Valency equal to 2. Consequently, DOE(Sa) = 40/2 = 20 g/mol. Aluminium (Al). Its atomic weight 26,98. (Rounded 27). Valence equal to 3. Thus, Mae(Al) = 27/3 = 9 g/mol.

3

These methods are applicable if we are talking about pure

**metal**X. But if they are part of a connection, for example, the same oxides? Here we must remember another rule: equivalent mass**of the oxide**is calculated by the formula: Me + Mo, where Mo is the equivalent mass of oxygen. It is, accordingly, calculated according to the formula already considered, that is, 16/2 = 8.4

Suppose you have a primary aluminium oxide, Al2O3. How to calculate equivalent weight? Very simple: 27/3 + 16/2 = 17 g/mol.

5

Is there another way to determine the equivalent mass

**of the metal**and its**oxide**? Yes, and very effective. It is based on the so-called law of equivalents, according to which all substances react with each other in equivalent quantities. For example: metal weight 33.4 grams entered into reaction of oxidation with oxygen. The result is an oxide with a total mass of 43 grams. You want to determine the equivalent*mass*of the**metal**and its**oxide**.6

First, calculate how much oxygen combines with the metal in the course of this reaction: 43 – 33,4 = 9.6 grams. According to the law of equivalents, this mass is as much larger than the equivalent

*mass*of oxygen (which, recall, is equal to 8), many times the equivalent mass**of the metal**is less than its original amount. That is 33,4/DOE(IU) = 9,6/8. Consequently, Me(me) = 33,4*8/9,6 = 27,833 g/mol, or about 27.8 g/mol. This is the equivalent mass**of the metal**.7

Equivalent weight

**of oxide**find the following: 27,8 + 8 = 35,8 g/mol.# Advice 5 : How to calculate the equivalent mass of

The equivalent mass, or molar mass equivalent, is the amount of material interacting with one mole of hydrogen or displacing the same number of atoms of hydrogen from its compounds. This is indicated by the value MEq, measured in g/mol, calculated according to the formulas or experimentally.

You will need

- - periodic system;
- calculator;
- - chemical utensils;
- - diluted hydrochloric acid;
- - hanging metal.

Instruction

1

To find the equivalent

**mass of**a simple substance, use the formula:MEq = MA/B, where MEq is the equivalent mass;MA is the atomic mass of an element; B is a valence.For example, according to the formula equivalent weight of sodium is equal 22,99 g/mol, and divalent sulfur – 32/2 = 16 g/mol, etc. For complex substances of molar mass equivalent will be called the amount of substance reacted without residue with one equivalent of another substance, such as hydrogen.2

Remember that the calculation of this quantity for different chemical compounds has nuances. For example, when calculating the equivalent mass of oxides – fold values of the equivalent masses of the components of the connection. For example, given the zinc oxide. First, consider MEq (Zn) = 65/2 =32,5 g/mol. Then MEq (O) = 16/2 = 8 g/mol. Thus, get an equivalent

**mass of**ZnO is equal to 40.5 g/mol. And calculate**the mass**equivalent of the acid is possible by dividing its molecular**weight**by the number of hydrogen atoms contained in it: MEq (H2SO4) = 98/2 = 49 g/mol, etc.3

For the experimental determination of the equivalent mass of the first follow safety precautions when working with acids and gases. Then take the burette, the tube and funnel. Connect them together with rubber tubes. Fill the burette with distilled water, using a funnel, set the level at zero.

4

Into test-tube pour 5 ml of hydrochloric acid (try not to soak the wall). On the dry wall place the mounting metal. Ensure that it does not fall into the acid ahead of time. Close the test tube with a cork and shake. The hydrogen will displace the water from the burette. After completion of the reaction level the water level in the burette and the funnel. Write down the final result, the temperature and pressure during the experiment.

5

Determine the displaced volume of hydrogen, by comparing the starting and ending water level in the burette. Give the result of normal conditions, using the readings of the barometer and thermometer. And then only calculate

**the weight**of metal equivalent, using the formula:m (metal)/V (hydrogen in the rules.conditions) = MEq.(metal)/Vэкв (hydrogen).