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)
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.
Outline a project which aims to find the dominant coat colour in dogs.
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?
How is the sex of the child determined in human beings?
(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.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
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?
What is hydrogenation? What is its industrial application?
What is meant by power of accommodation of the eye?
What do you mean by a precipitation reaction? Explain by giving examples.
Explain the terms analogous and homologous organs with examples.
Explain why the planets do not twinkle.
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
Can any source of energy be pollution-free? Why or why not?
What is the principle of an electric motor?
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary inside the coil?
Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?