A. The balanced chemical equation is correct:
k2co3 + 2hcl --> 2kcl + co2 + h2o
B. First let us calculate the moles of K2CO3.
moles K2CO3 = 3 g / (138.205 g/mol) = 0.0217 mol
From the equation, we need 2 moles of HCl per 1 mole of K2CO3, hence:
moles HCl needed = 0.0217 mol * 2 = 0.0434 mol
So the volume required is:
volume HCl = 0.0434 mol / 6 M = 7.24 x 10^-3 L = 7.24 mL
C. The number of moles of HCl and KCl is equal hence:
moles KCl = 0.0434 mol
The molar mass of KCl is 74.5513 g/mol, so the mass is:
mass KCl = 0.0434 mol * 74.5513 g/mol = 3.24 grams