Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
(a) Hydrogen gas combines with nitrogen to form ammonia
H2 + N2 ---------→ NH3
Hydrogen gas nitrogen gas Ammonia
3H2 + N2 -----------→ 3NH3
Hydrogen gas NItrogen gas Ammonia
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide
H2S(g) + O2(g) ----------------→ H2O(l) + SO2(g)
Hydrogen sulphide gas Oxygen (from air) water Sulpur dioxide
2H2S(g) + 3O2(g) --------------→ 2H2O(l) + 2SO2(g)
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate
BaCl2(aq) + Al2(SO4)3(aq) --------→ AlCl3(aq) + BaSO4(s)
Barium chloride Aluminium sulphate Aluminium chloride Barium sulphate
3BaCl2(aq) + Al2(SO4)3(aq) -------→ 2AlCl3(aq) + 3BaSO4(s)
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas
K(s) + H2O(l) -----→ KOH(aq) + H2(g)
Potassium Water potassium hydroxide hydrogen gas
2K(s) + 2H2O(l) ------- → 2KOH(q) + H2(g)
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
Outline a project which aims to find the dominant coat colour in dogs.
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
How is the sex of the child determined in human beings?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
What is an homologous series? Explain with an example.
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
Why is variation beneficial to the species but not necessarily for the individual?
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Compare the power used in the 2 Ω resistor in each of the following circuits:
(i) a 6 V battery in series with 1 Ω and 2 Ω resistors, and (ii) a 4 V battery in parallel with 12 Ω and 2 Ω resistors.
Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)
(a) mass (b) speed
(c) velocity (d) momentum
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south (b) towards east
(c) downward (d) upward
The magnification produced by a plane mirror is +1. What does this mean?
Explain why the planets do not twinkle.
Name a mirror that can give an erect and enlarged image of an object.