1. A 6.7 g sample of a mixture of hexane(C6H14) and unknown hydrocarbon was burnt in oxygen in a vessel. After the products were cooled, the vessel was found to contain 9.54g of water and 5.00L (at 300K and 234.4 K pa) of a mixture of gases which is 20% CO and 80% CO2 by volume.
a) Determine the emperical formula of the unknown hydrocarbon, given that its mass percent in the initial sample was 10.15%.
b) What volume of oxygen gas may used in this experiment ?
2. Mixing concentrated and dilute solutions to achieve the desired concentration of solute is a routine procedure.
Three different solutions of sodium bicarbonate A, B and C were used to prepare three mixtures (No: 1, 2, 3). Each of these mixtures was treated with an excess of hydro chloric acid.
The resulting carbon dioxide was collected and its volume measured.
| Mixture No. |
Mass of Solution |
Mass of solution |
Mass of solution |
Volume of gas evolved |
|
A(g) |
B(g) |
C(g) |
(S.T.P) dm3 |
| 1 |
150 |
100 |
50 |
8.92 |
| 2 |
150 |
100 |
150 |
12.09 |
| 3 |
100 |
100 |
100 |
8.85 |
A solution was prepared by mixing 100ml of each A, B and C solutions and diluted to final volume 500ml. 20 ml of this solution was taken in a
conical flask containing 5 ml water and was titrated with 0.1 NH2SO4.
What is the volume of acid required to neutralize the Na2CO3 present in the conical flask.
3. A mixture of nitrogen and hydrogen gases with a total volume of 0.500 dm3 (measured at S.T.P) was passed over a heated platinum catalyst. One half of the gaseous mixture containing product was bubbled through 10 cc of 4.39% aqueous solution of HCl with a density of 1.020 g/cm3. To neutralize excess acid, 8.30 cm3 of 0.5486M NaOH is required. The second half of the mixture was burnt in an excess of oxygen gas and the combustion products were passed through a column filled with P2O5. As a result, the mass of the column is increased by 0.08438g.
a) Calculate the mass percent of HCl in the solution before adding of NaOH.
b) Calculate the mass percent of nitrogen gas in the initial mixture.
4. A sample of 5g of technical iron (II) sulphide FeS which containing 5% metallic iron reacted with hydro chloric acid to produce FeCl2 and some gases. What is the percentage composition of the gas? This gas can be bubbled through 0.1 M copper sulphate solution. What should be the mass of copper precipitated from the solution if the solubility of copper sulphide is assumed to be zero.
5. Four reactions A, B, C and D were carried in the laboratory. They proceeded with different yields. One of the starting materials 'R' was same in all the four reactions, but products were different in each case. The 'X' was an element in the 'R' appeared only in one product in each case of reactions. a, b, c and d were the products those contain 'X' corresponding to the reactions A, B, C and D respectively. The molecular masses of R, a, b, c and d are 100, 200, 150, 120 and 140 respectively. The atomic mass of 'X' is 20 and its percentage by weight in 'R' is 20. Every one mole of R could give one mole of the compound that contain X in each case.
(i) If the percentage yields were 20%, 30%, 70%, 80% for A, B, C and D reactions respectively then the order of masses of a, b, c and d , with increasing amount of X , is
a) d, c, b, a
b) a, b, c, d
c) c, a, d, b
d) Not possible to predict
e) possible to predict but none of above orders mentioned in first three options. Give the suitable reason for your answer and show respective calculations.
(ii) Is it possible to determine mass of R must be taken to get one mole of each a, b, c and d with mentioned yields in the above problem ? If your answer is YES then give the suitable calculation, justifying your answer. If NO then identify the data that should be required to find the mass of R.
(iii)Is the mass ratios of a, b, c and d, if reactions proceed with above percentage yields and the mass of R that will be used is in the ratio
1 : 2 : 1: 2, possible to predict? If your answer is YES then give the suitable calculation, justifying your answer.