question_answer 30)

  Two chemical species X and Y combine together to form a product P which contains both X and and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct? (i) P is a compound                                                          (ii) X and Y are compounds (iii) X and Y are elements                                              (iv) P has a fixed composition (a) (i), (ii) and (iii)             (b) (i), (ii) and (iv)             (c) (ii), (iii) and (iv)           (d) (i), (iii) and (iv)

Answer:

  (d) In this reaction, X and Y can not be broken down into simpler substances by chemical reactions; therefore, X and v are elements. A compound is a substance made up of two or more elements chemically combined in a fixed proportion by mass. therefore, P is a compound, having a fixed composition.