Answer:
9.17 g
Explanation:
1) Calculate mols of PCl5
PCl5 (aq) + 4H2O (l) ⟶ H3PO4 (aq) + 5HCl (aq)
Mass of PCl5: 26.5g
Molar Mass of PCl5 208.24g/mol
Mol of PCl5 = Mass PCl5 /Molar mass PCl5  = 26.5g / (208.24g/mol) = 0.127257011 mol
2) Calculate mols of water needed to react
Mols of H2O per 1 Mols of PCl5 = 4 (because 4 water is needed to Phosphorus pentachloride).
Mols of H2O = Mol of PCl5 * 4 = 0.127257011 * 4 = 0.509028044 mols
3) Calculate Grams of water needed to react
Mols of H2O = 0.509028044 mols
Molar Mass of H2O = 18.015 g/mol
Mass of H2O = Mols of H2O * Molar Mass of H2O 
= 0.509028044 mols* 18.015 g/mol = 9.17014021 g
sf = 3
9.17 g
 
        
             
        
        
        
Answer:
Na+
Explanation:
The equation would be: 
HCl (aq) + NaOH (aq) --> HOH (l) + NaCl (aq)
The equation is already balanced and the NaCl will disassociate in Na+ and Cl- and HCl will disassociate into H+ and Cl- and NaOH will disassociate into Na+ and OH-. Na+ is on both sides of the equation and stays the same, so Na+ will be the spectator ion.  
 
        
                    
             
        
        
        
The fourth combination is not allowed.
The third quantum number, i.e. m subscript l, only may an integer number from -l to + l. Given that l = 0, the only allowed m subscript l is 0.
        
                    
             
        
        
        
Explanation:
if they aren't in a solvent, then you magnetize first, to remove the iron fillings, secondly, you can sieve to separate the sand and pebbles