Answer:
It is 20. g HF 
Explanation:
H2 + F2 ==> 2HF  ...  balanced equation
Since the question is asking us to find the mass of product formed, we will want to first convert the molecules of H2 into moles of H2 (we could do this at the end of the calculations, but it's just as easy to do it now).
moles of H2 present (using Avogadro's number):  
3.0x1023 molecules H2 x 1 mole H2/6.02x1023 molecules = 0.498 moles H2
From the balanced equation, we see that 1 mole H2 produces 2 moles HF.  Therefore, we can now find the theoretical mass of HF produced from 0.498 moles H2:
0.498 moles H2 x 2 moles HF/1 mol H2 = 0.996 moles HF formed.
The molar mass of HF = 20.01 g/mole, thus...
0.996 moles HF x 20.01 g/mole = 19.93 g HF = 20. g HF formed (to 2 significant figures)
 
        
             
        
        
        
The Gulf Stream, warm current in the Atlantic
        
                    
             
        
        
        
Please correct me if I'm wrong but I think the answer is b or c 
also sorry if i do get it wrong
        
             
        
        
        
Answer: -
The first step involves protonation of the carbonyl oxygen.
After protonation, the Alcohol oxygen now attacks the carbon of the carbonyl.
Thus a six membered ring is formed with 5 carbon atoms and 1 oxygen atom. The 1st position carbon atom has 2 OH groups.
One of these gets again protonated.
This leaves as water. With the loss of the H+, there results a carbonyl at 1 position. 
Thus 5-hydroxypentanoic acid forms a lactone or 2-oxanone in presence of acid.
 
        
             
        
        
        
Answer:
yes, because evidence from scientifically research studies, is important because it lets us make decisions based on what works with studies of science we can know if this is right or not  
Explanation:
Hope i helped~