Help! What is a multi-step mechanism? Please help me to solve this?

Identify the reaction intermediate or intermediates in the following multi-step mechanism. (Separate substances in a list with a comma.)
Overall: 2 NaCl + H2SO4 + CaCO3 + 2 C → Na2CO3 + CaS + 2 CO2 + 2 HCl

Step 1: 2 NaCl + H2SO4 → Na2SO4 + 2 HCl
Step 2: Na2SO4 + CaCO3 + 2 C → Na2CO3 + CaS + 2 CO2

1 Answer
Truong-Son N.
Feb 13, 2018

You're given the two-step mechanism. It is just supposed to add up to the overall reaction:

#2"NaCl"(aq) + "H"_2"SO"_4(aq) -> cancel("Na"_2"SO"_4(aq)) + 2"HCl"(aq)#

#ul(cancel("Na"_2"SO"_4(aq)) + "CaCO"_3(s) + 2"C"(s) -> "Na"_2"CO"_3(aq) + "CaS"(s) + 2"CO"_2(g))#

#2"NaCl"(s) + "H"_2"SO"_4(aq) + "CaCO"_3(s) + 2"C"(s) -> "Na"_2"CO"_3(aq) + "CaS"(s) + 2"CO"_2(g) + 2"HCl"(aq)#

The only intermediate is #"Na"_2"SO"_4(aq)#. It gets produced in step 1 and consumed in step 2. Is a catalyst present?

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