Question

Calculate the approximate number of atoms in a bacterium, assuming the average mass of an atom is ten times the mass of a hydrogen atom. The mass of a bacterium is 10−15 kg and the mass of a hydrogen atom is of the order of 10−27 kg.

Answer 1

Answer: -

The approximate number of atoms in a bacterium is 10¹¹

Explanation: -

We are given the mass of a bacterium is 10⁻¹⁵ kg.

We are told that the mass of a hydrogen atom is 10⁻²⁷ kg.

Finally we learn that the average mass of an atom of the bacterium is ten times the mass of a hydrogen atom.

Mass of an atom of bacterium = 10 x mass of hydrogen atom

                                                   = 10 x 10⁻²⁷ kg.

                                                   = 10⁻²⁶ kg.

Thus the number of atoms in a bacterium = $\frac{Total mass}{mass of 1 bacterium atom}$

                                                                      = $\frac{10-15 kg}{10-26 kg}$

                                                                      = 10¹¹