Chemistry
(a) A flask contains 3.2 g of sulphur dioxide. Calculate the following:
(i) The moles of sulphur dioxide present in the flask.
(ii) The number of molecules of sulphur dioxide present in the flask.
(iii) The volume occupied by 3.2 g of sulphur dioxide at S.T.P.
(b) An Experiment showed that in a lead chloride solution, 6.21 g of lead is combined with 4.26 g of chlorine. What is the empirical formula of this chlorine? (Pb = 207; Cl = 35.5)
Mole Concept
9 Likes
Answer
(a) (i) Molar mass of sulphur dioxide = 32 + 2(16) = 64 g
64 g of sulphur dioxide = 1 mole
So, 3.2 g = x 3.2 = 0.05 moles
(ii) 1 mole of SO2 = 6.02 × 1023 molecules
So, in 0.05 moles, no. of molecules = 6.02 × 1023 × 0.05 = 3 × 1022
(iii) The volume occupied by 64 g of SO2 = 22.4 dm3
3.2 g of SO2 will be occupied by volume
x 3.2 = 1.12 L
| (b) Element | Mass (g) | Atomic mass | Moles | Simplest ratio |
|---|---|---|---|---|
| Pb | 6.21 | 207 | = 0.03 | = 1 |
| Cl | 4.26 | 35.5 | = 0.12 | = 4 |
Simplest ratio of whole numbers Pb : Cl = 1 : 4
Hence, empirical formula is PbCl4
Answered By
4 Likes
Related Questions
10 g of a mixture of sodium chloride and anhydrous sodium sulphate is dissolved in water. An excess of barium chloride solution is added and 6.99 g of barium sulphate is precipitated according to the equation given below:
Na2SO4 + BaCl2 ⟶ BaSO4 + 2NaCl
Calculate the percentage of sodium sulphate in the original mixture.
When heated, potassium permanganate decomposes according to the following equation:
2KMnO4 ⟶ K2MnO4 + MnO2 + O2
(a) Some potassium permanganate was heated in the test tube. After collecting one litre of oxygen at room temperature, it was found that the test tube had undergone a loss in mass of 1.32 g. If one litre of hydrogen under the same conditions of temperature and pressure has a mass of 0.0825 g, calculate the relative molecular mass of oxygen.
(b) Given that the molecular mass of potassium permanganate is 158. What volume of oxygen (measured at room temperature) would be obtained by the complete decomposition of 15.8 g of potassium permanganate? (Molar volume at room temperature is 24 litres)
The volume of gases A, B, C and D are in the ratio, 1 : 2 : 2 : 4 under the same conditions of temperature and pressure .
(i) Which sample of gas contains the maximum number of molecules?
(ii) If the temperature and pressure of gas A are kept constant, then what will happen to the volume of A when the number of molecules is doubled?
(iii) If this ratio of gas volume refers to the reactants and products of a reaction, which gas law is being observed?
(iv) If the volume of A is actually 5.6 dm3 at S.T.P., calculate the number of molecules in the actual Volume of D at S.T.P. (Avogadro's number is 6 × 1023).
(v) Using your answer from (iv), state the mass of D if the gas is dinitrogen oxide (N2O)
The equations given below relate to the manufacture of sodium carbonate [Mol. wt. of Na2CO3 = 106]
(i) NaCl + NH3 + CO2 + H2O ⟶ NaHCO3 + NH4Cl
(ii) 2NaHCO3 ⟶ Na2CO3 + H2O + CO2
Equations (1) and (2) are based on the production of 21.2 g. of sodium carbonate.
(a) What mass of sodium hydrogen carbonate must be heated to give 21.2 g. of sodium carbonate
(b) To produce the mass of sodium hydrogen carbonate calculated in (a), what volume of carbon dioxide, measured at s.t.p., would be required.