What is the number of moles of O-atoms in 126 amu of `HNO_3` ?

What is the number of helium atoms in 1 mole He?

What will be the number of oxygen atoms in 1 mole of O_(2) ?

A sample of ammonium phosphate (NH_(3))_(4) PO_(4) contains 3.18 moles of H atoms. The number of moles of O atoms in the sample is

In the reduction of HNO_3 to N_2O the number of mole of electrons involved per mole of HNO_3 is:

In the reduction of HNO_(3) to N_(2)O the number of moles of electrons involved per mole of HNO_(3) is