Question

A 2.0 milliliter sample of NaOH solution is exactly

Answer 1

V ( NaOH) = 2.0 mL / 1000 => 0.002 L 
M( NaOH) = ?

V ( HCl) = 4.0 mL / 1000 => 0.004 L
M(HCl) = 3.0 M

number of moles HCl:

n = M x V

n = 3.0 x 0.004

n = 0.012 moles of HCl

Mole ratio:

HCl + NaOH = NaCl + H2O

1 mole HCl ----------- 1 mole NaOH
0.012 moles HCl ----- ?

moles NaOH = 0.012 x 1 / 1 => 0.012 moles

M = n / V

M = 0.012 / 0.002

= 6.0 M

hope this helps!