Caffiene has a molecular mass of `194`. If it contains `28.9%` by mass of nitrogen, number of atoms of nitrogen in one molecule of caffeine is :

Calculate mass of one atom of nitrogen in gram .

What is the mass of : 1 mole of nitrogen atoms ?

A sample of sodium has a mass of 46g. What is the mass of the same number of calcium atoms as sodium atoms present in given sample ?

Calculate the mass of 3.011 ( 10 *24 ) molecules of nitrogen gas.

Common salt obtained from sea-water contains 8.775% Na Cl by mass. The number of formula units of NaCl present in 25 g of this salt is :

A compound with molecular mass 180 is acylated with CH_3COCl to get a compound with molecular mass 390. The number of amino groups present per molecule of the former compound is

A coordination complex compound of cobalt has molecular formula containing five ammonia molecules, one nitro group and two chlorine atoms for one cobalt atom. One mole of this compound produces three mole ions in an aqueous solution. On reacting this solution with excess of silver nitrate solution, two moles of AgCl get precipitated. The formula of this compound would be

The mass number of an element is 18. It contains 7 electrons. What is the number of protons and neutrons in it ? What is the atomic number of the element ?