The balanced chemical equation is:
2H2 + O2 ---> 2H2O
We are given the amount of the product produced from the reaction. This will be the starting point for the calculations.
355 g H2O ( 1 mol H2O/ 18.02 g H2O) ( 1 mol O2 / 2 mol H2O ) ( 32 g O2 / 1 mol O2 ) = 315.205 g O2
        
             
        
        
        
The molecular weight of unknown gas : 23.46 g/mol
<h3>Further explanation</h3>
Given
A vessel contains 10% of oxygen and 90% of an unknown gas.
diffuses rate of mixed gas = 86 s 
diffuses rate of O₂ = 75 s
Required
the molecular weight of unknown gas (M)
Solution
The molecular weight of mixed gas :(M O₂=32 g/mol)

Graham's Law :

 
        
             
        
        
        
Answer:
None of these
Explanation:
Friedel–Craft reaction is a reaction involves the attachment of substituents to the benzene ring.
Mechanism of the reaction of methylbenzene with 1-chlorodecane in the presence of ether and aluminum chloride :
Step -1 : Generation of stable carbocation.
Aluminium chloride acts as Lewis acid which removes the chloride ion from the alkyl halide forming carbocation. The primary carbocation thus formed gets rearranged to secondary primary carbocation which is more stable due to hyperconjugation.
Step-2: Attack of the ring to the carbocation
The pi electrons of the ring behave as a nucleophile and attacks the carbocation. Since, the group attached on the benzene is methyl (+R effect) , the attack is from the ortho and the para positions. Para product is more stable due to less steric hinderance. 
The product formed is shown in mechanism does not mention in any of the options.
So, None of these is the answer
 
        
                    
             
        
        
        
Answer:
There are many properties that differentiate metals from non-metals. They are: Luster, conductivity of heat and electricity, physical strength i.e. Brittle or difficult to break, etc.
 
        
             
        
        
        
Answer:
Cosmology is a branch of astronomy that involves the origin and evolution of the universe, from the Big Bang to today and on into the future. According to NASA, the definition of cosmology is "the scientific study of the large scale properties of the universe as a whole."