How many molecules of ch4 are in 48.2g of theis compound?

1 mol of any substance is made of 6.022 x 10²³ units. These units could be atoms making up elements or molecules making up compounds. 
methane is CH₄, 1 mol of CH₄ is made of 6.022 x 10²³ molecules of methane
molar mass of CH₄ is 16 g/mol 
so 16 g of CH₄ is made of 6.022 x 10²³ CH₄ molecules
therefore 48.2 g of this compound is made of - 6.022 x 10²³ /16 x 48.2 = 1.81 x 10²⁴ molecules of methane 
there are 1.81 x 10²⁴ molecules of methane 

Most smaller stars don't have a radiative zone.