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O2, N2 are present in the ratio of 1: 4 by weight. The ratio of number of molecules is :
Let mass of O2= 1 g
∴ Mass of N2= 4g
No. of molecules of O2 = \(\frac{1}{32}\)
No. of molecules of N2 = \(\frac{4}{28}\)
Ratio of no. of molecules = \(\frac{1}{32}\) : \(\frac{4}{28}\) = \(\frac{1}{32}\) : \(\frac{1}{7}\)
= 7 : 32
The hydrogen phosphate of certain metal has formula MHPO4. The formula of metal chloride would be
Formula of metal phosphate is M++H+PO4––– .Valency of metal +2.Hence metal chloride is MCl2.
Number of moles of NaOH present in 2 litre of 0.5 M NaOH is:
Given V= 2L, Molarity = 0.5M, Moles =?
Molarity = \(\frac{No.ofmoles of solute}{V ofsolution in L}\) or 0.5 = \(\frac{Moles}{2}\)
∴ Moles = 2 ×0.5 = 1.0
How many moles of helium gas occupy 22.4 litre at 0°C and 1 atm pressure ?
22.4L of He at STP = 1 mole
How many atoms are contained in one mole of sucrose(C12H22O11)?
Total atoms in 1 molecule of C12H22O11= 12 + 22 + 11 = 45
∴ Total atoms in 1 mole of C12H22O11= 45 × 6.02 × 1023 atoms/mol.
The mass of a molecule of water is
Mass of one molecule of Water
= \(\frac{18}{6.023 \times 10^{23}}\)
=3 × 10-23g = 3 × 10-26kg
The number of molecules in 8.96 litre of a gas at 0ºC and 1 atm. pressure is approximately
At S.T.P. 22.4 litre of gas contains 6.023 × 1023 molecules
∴ molecules in 8.96 litre of gas
= \(\frac{6.023 \times 10^{23} \times 8.96}{22.4}\)
=24.08 × 1022
The number of moles of oxygen in one litre of air containing 21% oxygen by volume, under standard conditions are
21% of 1 litre is 0.21 litre.
22.4 litres = 1 mole at STP
∴ 0.21 litre = \(\frac{0.21}{22.4}\) = 0.0093
The number of water molecules present in a drop of water(volume 0.0018ml) at room temperature is
0.0018 ml = 0.0018 g = 0.0001 mole of water = 10-4 mole
∴ number of water molecules=6.023 × 1023 × 10-4
= 6.023 × 1019
Number of g of oxygen in 32.2 g Na2SO4.10 H2O is
M. Wt of Na2SO4.10 H2O is 322 g which contains 224 goxygen.
∴32.2 g will contain 22.4 g oxygen.