Science
It is important to balance the chemical equations to satisfy the law of conservation of mass. Which of the following statements of the law is incorrect?
- The total mass of the elements present in the reactants is equal to the total mass of the elements present in the products.
- The number of atoms of each element remains the same, before and after a chemical reaction.
- The chemical composition of the reactants is the same before and after the reaction.
- Mass can neither be created nor can it be destroyed in a chemical reaction.
Related Questions
Select from the following the statement which is true for bases.
- Bases are bitter and turn blue litmus red.
- Bases have a pH less than 7.
- Bases are sour and change red litmus to blue.
- Bases turn pink when a drop of phenolphthalein is added to them.
Study the following table and choose the correct option:
S.
No.Salt Parent Acid Parent Base Nature of Salt (a) Sodium Chloride HCl NaOH Basic (b) Sodium Carbonate H2CO3 NaOH Neutral (c) Sodium Sulphate H2SO4 NaOH Acidic (d) Sodium Acetate CH3COOH NaOH Basic Consider the following statements in connection with the functions of the blood vessels marked A and B in the diagram of a human heart as shown.
(i) Blood vessel A — It carries carbon dioxide rich blood from the lungs.
(ii) Blood vessel B — It carries oxygen rich blood from the lungs.
(iii) Blood vessel B — Left atrium relaxes as it receives blood from this blood vessel.
(iv) Blood vessel A — Right atrium has thick muscular wall as it has to pump blood to this blood vessel.
The correct statements are
- (i) and (ii) only
- (ii) and (iii) only
- (ii), (iii) and (iv)
- (i), (ii) and (iii)
In living organisms during respiration which of the following products are not formed if oxygen is not available?
- Carbon dioxide + Water
- Carbon dioxide + Alcohol
- Lactic acid + Alcohol
- Carbon dioxide + Lactic acid