Mole ratio for the reaction is 1:1
no of moles in NaOH that reacted= 1*21.17/1000=0.02117mols
molarity of HCl=0.02117*10/1000
=2.117M
All alkail metals react with halogens vigorously to produce salt. The alkali metal would loose an electron to form and ion with the halogen
Sodium chloride is the chemical name for salt and is composed of sodium and chlorine, so it is a compound.
Answer:
B - The energy of reactants is conserved.
D - the nuclei of atoms changes completely ( if that's the option)
Explanation:
When magnesium metal burns is heated i the air it forms magnesium oxide.The balanced chemical reaction is given as:

2 moles of magnesium metal when reacts with 1 moles of oxygen it gives 2 moles of magnesium oxide which is white in color.
Some times along with formation of magnesium oxide small amount of magnesium nitride also produced due to which magnesium oxide appears grey in color .The balanced chemical reaction is given as:

3 moles of magnesium combines with 1 mol of nitrogen gas to to give 1 mol of magnesium nitride.