Question 2 Page 40 - Chapter 3 Class 9 - Atoms And Molecules

Last updated at April 16, 2024 by

Calculate the formula unit masses of ZnO, Na 2 O, K 2 CO 3 , given atomic masses of Zn = 65 u,

Na = 23 u, K = 39 u, C = 12 u,and O = 16 u.

 

Answer

Formula unit mass of ZnO = 1x Atomic mass of Zn + 1 x Atomic mass of O

                                            = 1 x 65u + 1x16u

                                            = 65u+16u

                                            = 81u

 

Formula unit mass of Na 2 O = 2x Atomic mass of Na + 1 x Atomic mass of O

                                            = 2 x 23u + 1x16u

                                            = 46u+16u

                                            = 62u

 

Formula unit mass of K 2 CO 3 = 2x Atomic mass of K + 1 x Atomic mass of C + 3 x Atomic mass of O

                                            = 2 x 39u + 1x12u + 3 x 16u

                                            = 78u+12u + 48u

                                            = 138u

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