If 20.0 grams of ca combines completely with 16.0 grams of s to form a compound l, what is the percent composition of ca in the compound?

The %  composition of Ca  in  the compound  is   calculated as  below

%  composition of Ca =mass of Ca/mass  of CaS x100
mass of Ca=20 grams

calculate the mass of CaS  by

 first  write the reacting equation

Ca+ S = CaS

then find the moles of  each  element
moles=mass/molar mass

moles for Ca=  20g/ 40 g/mol = 0.5 moles
moles for S= 16g/32g/mol = 0.5 moles

since Ca and S has the  same moles  and the reacting ratio between          Ca :CaS  the  moles of CaS is also = 0.5 moles

mass of CaS= moles  of CaS x molar mass CaS
 =0.5 x72= 36 grams  of Cas

the %  composition is therefore = 20g/36g x100 = 55.6%

I’d have to say no because without oxygen in the water the fish would all be dead. so if you want to fish for dead fish, pick the ponds with the lowest oxygen concentrations.