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प्रश्न
Explain with examples what is meant by a 'mole' of a substance.
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उत्तर
A mole is the quantity of a substance whose mass in grams is equal in magnitude to the molecular mass of that substance in Daltons. Thus, the molecular mass of oxygen is 32 u, and therefore 32g oxygen is 1 mole of oxygen. The molecular mass of water is 18u. Therefore, 18g of water makes 1 mole of water.
1 mole of a compound is the mass of that substance in grams equal in magnitude to its molecular mass. The SI unit is mol.
Number of moles of substances (n) = `"Mass of substance in grams"/"Molecular mass of substance"`
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संबंधित प्रश्न
Calculate the molar mass of the following substance:
Ethyne, C2H2
What is the mass of 10 moles of sodium sulphite (Na2SO3)?
How many moles are 3.6 g of water ?
Fill in the following blanks :
64 g of oxygen gas contains ................ moles of oxygen atoms.
What is the mass of 5 moles of sodium carbonate (Na2CO3) ?
(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Prove the Following :
One mole of any gas contains th e same number of molecules.
Define the term.
Molar volume
Explain the term:
Mole
Two oxides of a metal (M) have 20.12% and 11.19% oxygen. The formula of the first oxide is MO. Determine the formula of the second oxide.
Calculate the number of moles and number of molecules present in 1.4 g of ethylene gas. What is the volume occupied by the same amount of ethylene?
Consider the following reaction and based on the reaction answer the questions that follow :
\[\ce{(NH4)2Cr2O7 ->[heat] N2(g) + 4H2O(g) + Cr2O3}\]
Calculate :
(i) The quantity in moles of (NH4)2Cr2O7 if 63 gm of (NH4)2Cr2O7 is heated.
(ii) The quantity in moles of nitrogen formed.
(iii) The volume in litres or dm3 of N2evolved at STP.
(iv) The mass in grams of Cr2O3 formed at the same time
[Atomic masses : H = 1, Cr=52, N=14]
A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure.
(a) Find the number of moles of hydrogen present
(b) What weight of CO2can the cylinder hold under similar conditions of temperature and pressure? (H = 1 C = 12, O = 16)
(c) If the number of molecules of hydrogen in the cylinder is X, calculate the number of CO2 molecules in the cylinder with the same conditions of temperature and pressure.
(d) State the law that helped you to arrive at the above result.
How many grams of CO2 is present in 0.1 mole of it?
The molecular formula for elemental sulphur is S8. In a sample of 5.12 g of sulphur:
How many moles of sulphur are present?
Four grams of caustic soda contains ______.
Correct the statement, if required.
One mole of chlorine contains 6.023 x 1010 atoms of chlorine.
How many grams are there in the following?
2 moles of the hydrogen molecule, H2.
Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12 g. Molar atomic mass of magnesium is 24g mol–1.
Deduce the number of molecules of the following compound in the given quantity.
8.8g carbon dioxide
If 0.2 mol of the following substance is required how many grams of that substance should be taken?
magnesium oxide
