I can't balance the last one

A. Synthesis
Mg+H2O -> NH3

B Decomposition
CuCO3 -> CuO + CO2

C. Single Displacement
Zn + 2HCl -> ZnCl2 +H2

D. Double Displacement
6KI+3Pb(NO3)2-> 6KNO3+6PbI

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A. No. This is not a valid equation. Double check your book or worksheet to make sure you have it written down correctly.

B. Good

C. Good

D. You should have PbI2 for one of the products, not PbI. Make the change and try again to balance. You should find it to be much easier.

Thank you I got it now :)