What were the limitations of Newlands’ Law of Octaves?
Limitations of Newlands’ law of octave are as follow:
(i) This law is only applicable upto the calcium element. Elements after calcium don’t possess the properties similar to that of first.
(ii) He assumed that only 56 elements exist in nature, no more element can be further discovered.
(iii) Newland’s adjusted 2 elements in the same slot to fit the element in the table. Eg. cobalt and nickel are placed in the same slot with columns having fluorine, chlorine and bromine which have completely different properties.
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?
How is food transported in plants?
How does phototropism occur in plants?
Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
(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?
Why is the use of iodised salt advisable?
What are the different ways in which glucose is oxidised to provide energy in various organisms?
Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
Metal | Iron(II) sulphate | Cooper(II) sulphate | Zinc sulphate | Silver nitrate |
A | No reaction | Displacement | ||
B | Displacement | No reaction | Displacement | |
C | No reaction | No reaction | No reaction | No reaction |
What are the differences between the transport of materials in xylem and phloem?
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.