English Medium कक्षा ९ - CBSE Question Bank Solutions for Science

Sound travels in air :

The sound waves travel fastest :

State two observations which show that atom is not indivisible.

The velocities of sound waves in four media P, Q, R and S are 18,000 km/h, 900 km/h, 0 km/h and 1200 km/h respectively. Which medium could be a liquid substance?

State the law of conservation of mass. Give one example to illustrate this law.

Which postulate of Dalton's atomic theory can explain the law of conservation of mass ?

What is an atom ? How do atoms usually exist ?

The law of conservation of mass was given by :

One nm is equal to :

An atom of element E contains 3 protons, 3 electrons and 4 neutrons :
(a) What is its atomic number?
(b) What is its mass number?
(c) Write the electronic configuration of the element E.
(d) State whether element E is a metal or non-metal. Why?
(e) What type of ion, cation or anion, will be formed by an atom of element E? Why
(f) Write the symbol of the ion formed by an atom of element E.
(g) What could element X be?

An atom of an element X may be written as `""_9^4"X"`
(a) What does the figure 9 indicate?
(b) What does the figure 4 indicate?
(c) What is the number of protons in atom X?
(d) What is the number of neutrons in atom X?
(e) What is the number of electrons in atom X?
(f) How many electrons are there in the outermost shell of an atom of element X?
(g) Write the symbol of ion formed by an atom of element X.

The electronic configuration of an element Z is 2, 8, 8.
(a) What is the atomic number of the element?
(b) State whether element Z is a metal or a non-metal.
(c) What type of ion (if any) will be formed by an atom of element Z? Why?
(d) What is special about the outermost electron shell of the atom of this element?
(e) Give the name and symbol of element Z.
(f) Name the group of elements to which Z belongs.

Copper sulphate reacts with sodium hydroxide to form a blue precipitate of copper hydroxide and sodium
sulphate. In an experiment, 15.95 g of copper sulphate reacted with 8.0 g of sodium hydroxide to form
9.75 g of copper hydroxide and 14.2 g of sodium sulphate. Which law of chemical combination is illustrated by this data ? Give reason for your choice.

Potassium chlorate decomposes, on heating, to form potassium chloride and oxygen. When 24.5 g of potassium chlorate is decomposed completely, then 14.9 g of potassium chloride is formed. Calculate the mass of oxygen formed. Which law of chemical combination have you used in solving this problem ?

For the symbols H, D and T, write the subatomic particles (protons, neutrons and electrons) found in each one of them.

Which of the following statement is correct about the atom of an element ?

An ionic compound will be formed by the combination of one of the following pairs of elements. This pair of elements is :

Find the mass of 2 moles of nitrogen atoms.

How many atoms are there in exactly 12 g of carbon-12 element ? (C = 12 u)

Calculate the number of moles in 12.044 × 1025 atoms of phosphorus.