Which of the following pairs have the same number of atoms? (A) 16g of O2 and 4g of H2 (B) 16g of O2 and 44g of CO2 (c) 28g of N2 and 32g of O2 (D) 12g of c and 23g of Na

This is a Multiple Choice Questions as classified in NCERT Exemplar Option(C), (D) (A) The number of moles is given by the following formula, Moles = M a s s M o l a r m a s s -----------(1) The number of moles of O2 is calculated by using equation (1) as follows, Moles of O2 = 16 g 32 g / m o l = 0.5 mol The number of atoms can be calculated as, number of moles n u m b e r o f a t o m s A v o g a d r o s n u m b e r -----------(2) On substituting the values in the equation (2) 0.5 mol = n u m b e r o f a t o m s 6.022 * 10 23 number of atoms = 0.5 * 6.022 * 1023 The number of moles of H2 is calculated by using equation (1) as follows, Moles of H2 = 4 g 2 g / m o l = 2 mol On substituting the values in the equation (2): 2 mol = n u m b e r o f a t o m s 6.022 * 10 23 number of atoms = 2 * 6.022 * 1023 (B) The number of moles of CO2 is calculated by using equation (1) as follows Moles of CO2 = 44 g 44 g / m o l = 1 mol On substituting the values in the equation (2), the number of atoms can be calculated as , 1 mol = n u m b e r o f a t o m s 6.022 * 10 23 number of atoms = 1 * 6.022 * 1023 (C) The number of moles of N2 is calculated by using equation (1) as follows, Moles of N2 = 28 g 28 g / m o l =1 mol On substituting the values in the equation (2), the number of molecules can be calculated as 1 mol = n u m b e r o f a t o m s 6.022 * 10 23 number of atoms = 1 * 6.022 * 1023 The number of moles of O2 is calculated by using equation (1) as follows, Moles of O2 = 32 g 32 g / m o l = 1 The number of atoms can be calculated as, number of moles n u m b e r o f a t o m s A v o g a d r o s n u m b e r - On substituting the values in the equation (2) 1 mol = n u m b e r o f a t o m s 6.022 * 10 23 number of atoms = 1 * 6.022 * 1023 (D) The number of moles of C is calculated by using equation (1) as follows, Moles of C = 12 g 12 g / m o l =1 mol On substituting the values in the equation (2), the number of molecules can be calculated as 1 mol = n u m b e r o f a t o m s 6.022 * 10 23 number of atoms = 1 * 6.022 * 1023 The number of moles of Na is calculated by using equation (1) as fo Moles of Na = 23 g 23 g / m o l =1 mol On substituting the values in the equation (2), the number of molecules can be calculated as 1 mol = n u m b e r o f a t o m s 6.022 * 10 23 number of atoms = 1 * 6.022 * 1023