According to law of conservation of mass the mass of D formed is 7g
Hope u liked the answer :)
Given : 
5g of A reacts with 6g B 
⇒ C and D are formed where C is 4g 

need to find out : 
the weight of D

solution : 
according to the law of conservation of mass - 
⇒ mass of products = mass of reactants of chemical reaction 

mass of reactants = 5g + 6g 
                              = 11g 

let the weight of D be X 
⇒ 4g + X = 11g 
⇒ X = 11g - 4g 
⇒ X = 7g 

∴ the weight of D = 7g
2 5 2
hope so my answer is useful and smash # click the thanks button plz