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Atoms And Molecules
Question
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A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity.

Answer

Given, a stone is released from the top of a tower. 
Initial velocity, u = 0 m/s
Acceleration due to gravity, g = -9.8 m/s2 
Distance covered by the ball during the course of it's motion = 19.6 m 
Now, usign the equation of motion, 
                   v2 - u2 = 2ags
We have,
     v2 - 02 = 2 * (-9.8) * (-19.6) 
i.e.,  v2 - 02 = (19.6)2 
i.e.,   v = - 19.6 m/s
The negative sign indicates that the velocity is acting in the downward direction

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Some More Questions From Atoms And Molecules Chapter

Give the names of the elements in the following compounds.

(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder 
(d) Potassium sulphate.

Calculate the molar mass of the following substances:

(a) Ethylene
(b) Sulphur molecule, S8
(c) Phosphorus molecule, P4
(d) Hydrochloric acid, HCl
(e) Nitric acid, HNO3.

What is the mass of:

(a) 1 mole of nitrogen atoms

(b) 4 moles of aluminium atoms

(c) 10 moles of sodium sulphite.

Convert into mole

(a) 12 gm of oxygen gas

(b) 20 gm of water

(c) 22 gm of carbon dioxide.

What is the mass of?

(a) 0.2 mole oxygen atoms.

(b) 0.5 mole of water molecules.

Calculate the number of molecules of sulphur (S8) present in 16 gm of solid sulphur.

Calculate the number of aluminium ions present in 0.56 gm of aluminium oxide.

Explain law of conservation of mass.

50 g of 10% lead nitrate is mixed with 50 g of 10% sodium chloride in a closed vessel. After the reaction has taken place, it was found that 6.83 g of lead chloride was precipitated. Besides, the reaction mixture contained 90 g water and sodium nitrate. Calculate the amount of sodium nitrate formed.

Name and explain two important laws of chemical combination ?