Can you please answer the following board questions???
1) On what basis is a chemical eqation balanced?
2) BalancePb(NO3) -> PbO + NO2 + O2
3)What happens when hydrogen combines with oxygen in the presence of of an electric current?
4) Name the process in which the gain of electrons takes place?
5) How will you define a reducing agent?
6) Why do gold and platinum not corrode in moist air?
7) What happens when an aqueous solution of sodium sulphate reacts with an aqueous solution of barium chloride? state the physical condition of the reactants in which the reaction between them will not take place. Write the balanced chemical equation for the reaction and name the type of reaction.
8) Write any two observations in an activity may suggest that a chemical reaction has taken place. Give an example in support of your answer.
Due to paucity of time it would not be possible for us to provide the answers to all your queries. We are providing solutions to some your good queries. Try solving rest of the questions yourself and if you face any difficulty then do get back to us.
(1). The balancing of chemical equation is based on law of conservation of mass, which states that mass can neither be created nor destroyed. Thus, in a chemical reaction, the total mass of the reactants should be equal to the total mass of the products. This means that the total number of atoms of each element should be equal on both sides of a chemical equation. Such an equation is called a balanced chemical equation and the method by which it is obtained is called balancing of chemical equations.
(2) The balanced chemical equation is :
2Pb(NO3)2 → 2PbO + 4NO2 + O2.
(3). Hydrogen combines with Oxygen under electric current, to form water. The chemical equation can be written as:
2H2 + O2 → 2H2O
For the rest of the questions you can refer to the solved board paper section on our website, at the following link:
http://cbse.meritnation.com/cbse-science/model-papers/10/-1/modeltests.html