You have 1.0 L of a solution is 0.10 M in HCHO2. Which of the following solutions below, when added to that solution, will make a buffer.
a) 1.0 L of water
b) 0.10 moles of NaCHO2
c) 0.1 moles of NaCl
d) 0.1 moles of NaCl and 0.1 moles of NaCHO2
e) 0.1 moles of NaCH3CO2