one mole quantities of different substances have differnt masses meansured in gram
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Answer:
Amounts of Substances in Various Units
Amounts of substances are measured in units of mass (g or kg), volume (L) and mole (mol). Unit interconversions are based on the definitions of the units, and converting amounts from g or kg into mol is based on atomic masses of the elements.
Atomic masses are the masses of one mole of elements. A mole of any element has an Avogadro's number of atoms (= 6.02x1023 atoms per mole).
The natural units of substances are molecules, which are groups of atoms bonded together, except monatomic molecules of inert gases, He , Ne , Ar , Kr , Xe , and Rn . For example, molecules of oxygen, water, and phosphorous are O2 , H2O , and P4 respectively. These molecules have 2, 3, and 4 atoms respectively. Masses of one mole of substances are called molecular weights. Atomic and molecular weights are called molar masses.
The above illustrates only a very small number of examples. There are millions of compounds in the world. Please think of some other compounds you know of, and write down their formulas. Then figure out the number of atoms in each mole of your compounds.
Different substances have different molecular masses. Thus, equal masses have different numbers of atoms, molecules, or moles. On the other hand, equal numbers of moles of different substances have different masses. The stoichiometric relationships among reactants and products may be complicated in units of g, but much simpler relationships are seen if we deal with units of moles or natural units of atoms and molecules.
Moles (mol) represent amounts of substances in the unit of Avogadro's number (6.022x1023) of atoms and molecules. Since empirical formulas such as Fe2+ ions and Fe2O3 are used for ionic compounds, a mole represent Avogadro's number of ions or per formula as written. A mole of Fe2+ has 6.022x1023 ions, and a mole of Fe2O3 has 1.204x1024 Fe and 1.8066x1024 O atoms, a total of 3.0x1024 Fe and O atoms.
The mole unit is very important for chemical reactions, as is the skill to convert masses in g to mol. The number of moles of a substance in a sample is the mass in g divided by the molar mass, which gives the amount in moles.
mole=mass(g)molarmass(g/mol)
Another common measure of substances is volume. Since density is the mass divided by its volume, conversion between volume and mass is accomplished by the formula:
density=mass(g)volume(cm3)
mass=density(gcm−3)×volume(cm3)
These fundamental formulas are results of the definition of these terms.
Explanation:
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The mole (symbol: mol) is the unit of measurement for amount of substance in the International System of Units (SI). A mole of a substance[1] or a mole of particles[2] is defined as exactly 6.02214076×1023 particles, which may be atoms, molecules, ions, or electrons.[1] In short, for particles 1 mol = 6.02214076×1023.[3][2]
Mole
Unit system
SI base unit
Unit of
Amount of substance
Symbol
mol
Conversions
1 mol in ...
... is equal to ...
SI base units
Base unit (Dimensionless)
The definition was adopted in November 2018 as one of the seven SI base units,[1] revising the previous definition that specified it as the number of atoms in 12 grams of carbon-12 (12C), an isotope of carbon.
The number 6.02214076×1023 (the Avogadro number) was chosen so that the mass of one mole of a chemical compound, in grams, is numerically equal (for most practical purposes) to the average mass of one molecule of the compound, in daltons. Thus, for example, one mole of water contains 6.02214076×1023 molecules, whose total mass is about 18.015 grams – and the mean mass of one molecule of water is about 18.015 daltons.
The mole is widely used in chemistry as a convenient way to express amounts of reactants and products of chemical reactions. For example, the chemical equation 2H2 + O2 → 2H2O can be interpreted to mean that 2 mol dihydrogen (H2) and 1 mol dioxygen (O2) react to form 2 mol water (H2O). The mole may also be used to represent the number of atoms, ions, electrons, or other entities.[2] The concentration of a solution is commonly expressed by its molarity, defined as the amount of dissolved substance per unit volume of solution, for which the unit typically used is moles per litre (mol/l), commonly abbreviated M.
The term gram-molecule (g mol) was formerly used for "mole of molecules",[4] and gram-atom (g atom) for "mole of atoms". For example, 1 mole of MgBr2 is 1 gram-molecule of MgBr2 but 3 gram-atoms of MgBr2.[5][6]......
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