To find mol of substance, you need to remember a very simple rule: the mass of one mole of any substance is numerically equal to its molecular weight, only expressed in other units. And how is the molecular weight? Using the periodic table you will learn the atomic mass of each element in molecule of the substance. Next you need to fold the mass of an atom with the index of each element and get a response.
For example, widely used in agriculture fertilizer, ammonium nitrate (or different ammonium nitrate). The formula of this substance NH4NO3. How to determine what is it mol? First of all, write down an empirical (total) formula of the substance: N2H4O3.
Calculate its molecular weight given the index of each element: 12*2 + 1*4 + 16*3 = 76 .e.m. (atomic mass units). Therefore, its molar mass (i.e. the mass of one mole) is 76, only its dimension: gram/mole. Answer: one mole of ammonium nitrate weighs 76 grams.
Suppose you are given such a task. We know that the mass 179,2 liters of a gas is 352 grams. You must determine what is the weight of one mole of the gas. It is known that under normal conditions one mole of any gas or mixture of gases occupies a volume of approximately 22.4 liters. And you 179,2 liters. Perform a calculation: 179,2/22,4 = 8. Consequently, this volume contains 8 moles of gas.
Dividing the known conditions of the problem a lot on the number of moles, we obtain: 352/8 = 44. Therefore, one mole of the gas weighs 44 grams is carbon dioxide, CO2.
If there is some amount of gas of mass M enclosed in a volume V at a given temperature T and pressure P. it is Required to determine its molar mass (that is, to find out what is its mol). To solve the problem will help you a universal equation Mendeleev-Clapeyron: PV = MRT/m, where m is the same molar mass, which we need to determine and R is the universal gas constant, equal to 8,31. Transforming the equation, we get: m = MRT/PV. Substituting in the formula the known values, you will find, what is a mole of gas.
In the calculations of the commonly used rounded values of the atomic weights of the elements. If you require more precision, then rounding is unacceptable.
Advice 2: How to bring food moths
Food moths can be got even in the cleanest kitchen. It normally occurs in cereals and dry foods that are stored for quite a long time. Mol breed is very active, so bring this insect is not easy. But, if you approach the fight comprehensively to get rid of food moths possible.
If you find yourself in the kitchen food moths, please review and go through all the cereals, muesli, cereal, dried fruits, spices and other similar products. The eggs of this pest is similar to the network of the web, larva with black head, with a size of about 1 cm Without regret, dispose of contaminated supplies. To save them it is impossible, and the mole will move to other products even if they are stored in closed packaging – they are for moths, not obstacle, with the exception of glass and metal.
Remove all containers of supplies out of the drawers and lockers, set on the table. Thoroughly wipe all surfaces of the shelf water with vinegar or lemon juice. Open the Windows. Let the kitchen penetrate light and fresh air. Mole does not like them. Leave drawers and Cabinet doors open for 2-3 hours. Then lay the cabinets and drawers lavender flowers, orange and lemon peel - food moths cannot tolerate their smell. Also a good remedy against this pest is garlic. You can put one unpeeled clove in each container of cereal.
Not superfluous to install anywhere special traps for food moths, you can buy them in hardware stores. The device is similar to the triangle with the sticky viscera. Trap the smell of pheromones, the moths on the scent, and sticks. One trap is enough for about 8 weeks. They should be changed periodically. Even when the mole will disappear of the device it is better not to remove one or two of the pest will continue to fly for a long time.
It is easier not to fight appeared in the kitchen food moths, and to prevent its spread. For this we need not to stock a lot of products in store. It is best to store dry food in tightly sealed glass jars. After you brought flour or cereal from the store, put it on a few hours in the freezer. But the best option is to store all the bulk supplies in the fridge.
Advice 3: How to find the number of mol
In chemical processes involves the smallest particles of matter – atoms, molecules, ions, electrons. The number of such particles even in a very small amount of the sample to be investigated is extremely large. In order to avoid mathematical calculations with huge numbers, has introduced a special unit – the mole.
You will need
- - the periodic table.
A mole is the amount of substance that contains a certain number of particles (atoms, ions, molecules) equal to the Avogadro constant. Na = 6,02 X 10 to the 23. Itself the Avogadro constant is defined as the number of atoms contained in twelve grams of carbon.
Therefore, it is possible to calculate the number of moles contained in the substance, if you know the number of atoms or molecules in it. This value must be divided by Avogadro's number. For example, if in the sample there is of 12.04 x 10 23 molecules, then the number of moles will be 2. Indicated by the number of moles as n.
The molar mass of the substance (M) is mass, which has one mole of this substance. To obtain these data, using the periodic table. You need to add the molar mass of each element, taking into account existing ratios. For example, for methane CH4 molar mass M is equal to 12 + 4 x 1 = 16. This value is measured in grams divided by moles.
In order to calculate the mol, in addition to molar mass and know the mass of the test specimen. Further calculations are carried out according to the formula n = m/M where m is the mass of the substance.
If you know the concentration and volume of solution, we can find the number of moles of a substance, based on these data. For this you need to multiply the volume and concentration. The formula is as follows: n = c x V.
If you want to calculate the number of moles contained in the gas under normal conditions (pressure equal to 101 325 PA and a temperature of 273 K), you need to know is the volume of gas. The formula in this case is: n = V/Vm. Vm is the molar volume of an ideal gas, a constant value under normal conditions. Equal molar volume of 22.4 liters/mol. Often it is measured in cubic decimeters, divided by the mol.
Advice 4: What is the mole in chemistry
Chemicals can be measured in kilograms or milliliters, but in moles. Mole – unit of amount of substance, which appeared due to the fact that substances are composed of molecules and atoms.
What is a mole in chemistry: definition
The mole represents a quantity of a substance that contains as many particles (molecules or atoms) how many atoms contained in 12 g of carbon C. to find the number of particles in 12 grams of carbon, it is necessary to divide the total mass of the substance (0,012 kg) on the absolute mass of the carbon atom, component 19,93x10^(-27) kg.
The result is 6,02x10^23 particles. Found the number equal to the number of molecules or atoms in one mole of any substance is called Avogadro's number. Its dimension is 1/mol, or mol "to the minus one".
If the chemical substance consists of molecules in one mole of this substance would contain 6,02x10^23 molecules. So, 1 mole of hydrogen H2 is 6,02x10^23 molecules of H2, 1 mole of water H2O is 6,02x10^23 molecules H2O 1 mole of glucose C6H12O6 is 6,02x10^23 molecules of C6H12O6.
If the substance consists of atoms in one mole of that substance will contain the same Avogadro the number of atoms is 6,02x10^23. This applies, for example, 1 pray of iron Fe or sulfur S.
As evidenced by the amount of substance
So, 1 mole of any chemical substance contains Avogadro the number of particles constituting a given substance, i.e. about 6,02x10^23 molecules or atoms. The total amount of substance (number of moles) is denoted by the Latin letter " n " or the Greek letter "nu". It can be found against the total number of molecules or atoms of a substance to the number of molecules in 1 mole the Avogadro number:
n=n/N(A), where n – amount of substance (mol), N is the number of particles, N(A) is Avogadro's number.
Hence it is possible to Express the number of particles in a given volume of a substance:
N=N(A) x n.
The actual mass of one mole of a substance is called its molar mass and represent the mean M. It is expressed in "grams per mole" (g/mol), but is numerically equal to relative molecular mass Mr of a substance (if the substance consists of molecules) or relative atomic mass Ar of substance, if the substance consists of atoms.
The relative atomic masses of elements can be found on the periodic table (typically, when calculations are rounded). So, for hydrogen is 1, for lithium – 7, carbon – 12, oxygen – 16, etc. Relative molecular mass are formed from the relative atomic masses of the constituent molecules of atoms. For example, the relative molecular mass of water H2O
Relative atomic and molecular mass is a dimensionless value, expressed as the mass of the atom and the molecule relative to conventional unit – 1/12 the mass of an atom of carbon.
In the model task is usually required to find the number of molecules or atoms into a given amount of substance which mass is a given amount of substance, number of molecules in a given mass. It is important to understand that the molecular formula of a substance indicates the number of moles of each element included in its composition. That is, 1 mol of H2SO4 contains 2 moles of hydrogen atoms H 1 mole of sulfur atoms S, 4 moles of oxygen atoms O.