Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
Element | K L M |
Nitrogen Phosphorus |
2 5 2 8 5 |
Nitrogen is more electronegative than phosphorus. As we move down a group, the number of shells increases. Therefore, the valence electrons move away from the nucleus and the effective nuclear charge decreases. Resulting in a decrease in the tendency to attract electrons and hence electronegativity decreases.
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?
Explain the mechanism of the cleaning action of soaps.
How would you distinguish experimentally between an alcohol and a carboxylic acid?
What is ozone and how does it affect any ecosystem?
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(a) is zero.
(b) decreases as we move towards its end.
(c) increases as we move towards its end.
(d) is the same at all points.
What processes would you consider essential for maintaining life?
Outline a project which aims to find the dominant coat colour in dogs.
How is oxygen and carbon dioxide transported in human beings?
How are the lungs designed in human beings to maximise the area for exchange of gases?
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?