Use Mendeléev’s Periodic Table to predict the formulae for the oxides of the following elements:
K, C, AI, Si, Ba.
The formulae for oxide s of elements are:
K is in group 1. So, the oxide will be K2O.
C is in group 4. So, the oxide will be CO2.
Al is in group 3. So, the oxide will be Al2O3.
Si is in group 4. So, the oxide will be SiO2.
Ba is in group 2. So, the oxide will be BaO.
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?
Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
(b) Zinc + Silver nitrate → Zinc nitrate + Silver
(c) Aluminium + Copper chloride → Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Explain the terms analogous and homologous organs with examples.
In Activity 13.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?
What will be the formula and electron dot structure of cyclopentane?
Name two safety measures commonly used in electric circuits and appliances.
Outline a project which aims to find the dominant coat colour in dogs.
What will happen if we kill all the organisms in one trophic level?
How would you distinguish experimentally between an alcohol and a carboxylic acid?
What were the limitations of Döbereiner’s classification?