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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:
Sulphur molecule, S8
What is the mass of 0.5 mole of water molecules?
A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure
1) Find the number of moles of hydrogen present.
2) What weight of CO2 can the cylinder hold under similar conditions of temperature and pressure? (H = 1, C = 12, O = 16)
3) If the number of molecules of hydrogen in the cylinder is X, calculate the number of CO2 molecules in the cylinder under the same conditions of temperature and pressure.
4) State the law that helped you to arrive at the above result.
One of the following elements has an atomicity of ‘one’. This element is :
Show by means of calculations that 5 moles of CO2 and 5 moles of H2O do not have the same mass. How much is the difference in their masses ?
Calculate the mole ratio of 240 g of calcium and 240 g of magnesium. (Ca = 40 u ; Mg = 24 u)
Which of the following pair of elements represents a mole ratio of 1 : 1 ?
If 0.2 mol of the following substance is required how many grams of that substance should be taken?
Sodium chloride
What is the value of Avogadro's number?
Explain the term:
Mole
Calculate the weight of one molecule of oxygen.
[Avogadro’s number = 6 × 1023, O = 16 ]
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]
How many grams of CO2 is present in 0.1 mole of it?
Calculate the number of atoms in the following:
52 g of He
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1 mole of any substance contains ______ molecules.
Calcium chloride when dissolved in water dissociates into its ions according to the following equation.
\[\ce{CaCl2} (aq) → {Ca^{2+} (aq) + 2{Cl}- (aq)}\]
Calculate the number of ions obtained from CaCl2 when 222 g of it is dissolved in water.
Deduce the number of molecules of the following compound in the given quantity.
90g water
Deduce the number of molecules of the following compound in the given quantity.
8.8g carbon dioxide
