A mixture of iron and sulphur can be separated by dissolving the mixture in?
A. steam
B. dilute hydrochloric acid
C. dilute sodium hydroxide
D. benzene
D
3.
A given amount of gas occupies 10.0 dm3 at atm, and 273°C. The number of moles of the gas present is? (Molar volume of a gas at s.t.p. = 22.4 dm3)
A. 0.89 mol
B. 1.90 mol
C. 3.80 mol
D. 5.70 mol
B
4.
8.0 g of an element X react with an excess of copper (ll) tetraoxosulphate (lV) solution to deposit 21.3 g of copper. The correct equation for the reaction is?
(Cu = 64).
A. X(s) + CuSO4(aq) → Cu(s) + XSO4(aq)
B. X(s) + 2CuSO4(aq) → 2Cu(s) + X(SO4)2(aq)
C. 2X(s) + CuSO4(aq) → Cu(s) + X2SO4(aq)
D. 2X(s) + 3CuSO4(aq) → 3Cu(s) + X2(SO4)3(aq)
A
5.
C3H8(g) + 502(g) → 4H2O + 3CO2(g). Form the equation above the volume of oxygen at s.t.p. required to burn 50cm3 of propane is?
C3H8 + 502 → 4H2O + 3CO2. From the equation above 1 dm3 of C3H8 require 5dm3 of O2 at s.t.p. ∴ 50cm3 of C3H8 require x = (50) / (1000) x 5 x 1 x = (250) / (1000) x = 250cm
30cm3 of hydrogen was collected over water at 27°C and 780 mm Hg. If the vapour pressure of water at the temperature of the experiment was 10 mm Hg, calculate the volume of the gas at 760 mm Hg and 7°C?
If sulphur (IV) oxide and methane are released simultaneously at the opposite ends of a narrow tube, the rates of diffusion Rso2 and Rch4 will be in the ratio?
(S = 32, O = 16, C = 12, H = 1)
A. 4:1
B. 2:1
C. 1:2
D. 1:4
C
8.
A solid begins to melt when?
A. constituent particles acquires a greater kinetic energy
B. energy of vibration of particles of the solid is less than the intermolecular forces
C. constituent particles acquires energy above the average kinetic energy
D. energy of vibration of particles of the solid equals the intermolecular forces
When a solid is heated, the particles are given more energy and start to vibrate faster. At a certain temperature, the particles vibrate so much that their ordered structure breaks down. At this point the solid melts into liquid.