Long Answer Type
Short Answer TypeClassify the following as pure substances or mixtures: air, milk, graphite, diamond, gasoline, tap water, distilled water, oxygen, one rupee coin, 22 carat gold, steel, iron, sodium chloride, iodized table salt.
Separate the following substances into elements and compounds: Graphite, Diamond, Distilled water, Oxygen, Iron, Sodium chloride, Blue vitriol.
How will you separate the following mixtures?
(i) Oil and water
(ii) Iron-filings and saw dust.
(iii) Glass powder and sugar.
Long Answer TypeShort Answer TypeIf 6.3g of NaHCO3 are added to 15.0 g of CH3COOH solution, the residue is found to weigh 18.0g. What is the mass of CO2 released in the reaction?
Long Answer TypeState the law of constant composition or Definite proportion. Explain with suitable examples.
Law of constant composition (Louis Proust, 1799) states that a pure chemical compound, regardless of its source, is always made up of the same elements, combined together in a fixed proportion by weight.
For example, carbon dioxide can be obtained by a number of methods:
(i) by burning coal or candle
(ii) by respiration
(iii) by heating limestone (CaCO3)
(iv) by the action of dilute hydrochloric acid on marble pieces.
It has been observed that each sample of carbon dioxide contains carbon and oxygen elements in the ratio of 3:8 by weight.
In an experiment 4.68 g iron oxide on reduction with hydrogen yields 3.86 g of iron. In another experiment 3.88 g of iron oxide gives 3.2 g of iron on reduction with hydrogen. Prove that the above data illustrates the law of constant proportions.
Weight of copper oxide obtained by treating 2.16 g of metallic copper with nitric acid and subsequent ignition was 2·7g. In another experiment, 1 · 15 g of copper oxide on reduction yielded 0·92g of copper. Show that the result illustrates the law of definite proportion.
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