k2co 3+h2so 4 = k2co 4+H2O+CO2↑
138 44
X 6.6g g
138:x=44:6.6g？
x=20.7g？
(2) 20.7g××100% =11.7g.
The mass fraction of potassium in plant ash is ×100% =11.7%.
A: The mass of potassium carbonate is 20.7g, and the mass fraction of potassium element is 1 1 .70%.