Answer:
20 mL
Given data:
Molarity of NaCl = 0.100 M
Volume of Pb(NO₃)₂ = 5.00 mL (5.0/1000 = 0.005 L)
Molarity of Pb(NO₃)₂ = 0.200 M
Volume of NaCl needed = ?
Solution:
Chemical equation:
2NaCl + Pb(NO₃)₂ → PbCl₂ + 2NaNO₃
Number of moles of Pb(NO₃)₂:
Molarity = number of moles / volume in L
0.200 M = number of moles / 0.005 L
Number of moles = 0.200 M ×volume in L
Number of moles = 0.001 mol
now we will compare the moles of NaCl and Pb(NO₃)₂.
Pb(NO₃)₂ : NaCl
1 : 2
0.001 : 2/1×0.001 = 0.002 mol
Volume of NaCl:
Molarity = number of moles / volume in L
0.100 M = 0.002 mol / volume in L
Volume in L = 0.002 mol / 0.100 M
Volume in L = 0.02 L
volume in mL:
0.02 L × 1000 mL/1 L
20 mL