What is a balanced chemical equation? Wh | Class 10 Science Chapter Chemical reaction and Equation, Chemical reaction and Equation NCERT Solutions

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.

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 an homologous series? Explain with an example.

Why is variation beneficial to the species but not necessarily for the individual?

In evolutionary terms, we have more in common with

(a) a Chinese school-boy.
(b) a chimpanzee.
(c) a spider.
(d) a bacterium.

At the time of short circuit, the current in the circuit

(a) reduces substantially.
(b) does not change.
(c) increases heavily.
(d) vary continuously.

What is the difference between displacement and double displacement reactions? Write equations for these reactions.

Draw the diagram of a flower and label the four whorls. Write the names of gamete producing organs in the flower.

In the Modern Periodic Table, which are the metals among the first ten elements?

What are oxidising agents?

What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.

State the principle of an electric generator.

A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

What happens at the synapse between two neurons?