Stoichiometry

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Q:-What is stoichiometry?

Ans:-This word has been derived from a Greek word, which means to measure an element. The calculation of relative amounts of substances in a chemical reaction is called stoichiometry. The coefficients of balanced chemical equation are called stoichiometric coefficients.E.g.

NaCl + AgNO3 → AgCl + NaNO3
(58.5g) (170g) (143.5g) (85g)

LIMITING REAGENT

The reactant that is present in lesser amount and is completely consumed in the reaction is known limiting reagent. E.g. In the combustion of methane with oxygen, methane is the limiting reactant because it is completely consumed whereas oxygen is present in excess and is left unreacted.

NUMERICALS:STOICHIOMETRY

1) For the reaction :How many moles of C will be produced by 5 moles of A and 12 moles of B .Also identify the limiting reagent.

A + 2B → 4C.

Ans:-20 mol of C; A is the limiting reagent.

2) For the reaction:How many moles of C will be produced by 5 moles of A and 8 moles of B .Also identify the limiting reagent.

A + 2B → 4C.

Ans:-4 mol of C; B is the limiting reagent

3)For the reaction:How many moles of oxygen will be produced from 6.2 moles of water ?

2H₂ O → 2H₂ + O₂

(Ans:- 3.1 moles of oxygen) (note :- use conversion factor method.)

4) In the following reaction,How many moles of water will be required to make 19.2 moles of oxygen.

2H₂ + O₂ → 2H₂O

(Ans:- 38.4 moles of water) (note use conversion factor)

5) Consider the reaction, How many moles of oxygen are needed to combine with 8.4 moles of Hydrogen sulphide?

2H₂S + 3O₂ → 2H₂O + 2SO₂

(Ans :-12.6 moles of oxygen) (use conversion factor method)

6) In the following reaction,starting from 9.2 moles of oxygen, how many moles of H₂S will you need and how many moles of SO₂ will you get ?

2H₂S + 3O₂ → 2H₂O + 2SO₂

(Ans:- 6.13 moles of H2S are needed and 6.13 moles of SO2 moles we get).

7) Consider the reaction ,How many moles of oxygen are needed to react with 7.2 moles of propane.

C₃H₈ + 5O₂ → 4H₂O + 3CO₂

(Ans:- 36 moles of oxygen)

8)Consider the reaction,How many moles of propane and oxygen are needed to make 13.5 moles of CO2 ?

C₃H₈ + 5O₂ → 4H₂O + 3CO₂

(Ans :-4.5 moles of propane is needed and 22.5 moles of oxygen )

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