<Tr> <Td> Barium chloride </Td> <Td> Solid </Td> <Td> BaCl </Td> <Td> − 858.6 </Td> </Tr> <Tr> <Td> Barium carbonate </Td> <Td> Solid </Td> <Td> BaCO </Td> <Td> − 1213 </Td> </Tr> <Tr> <Td> Barium hydroxide </Td> <Td> Solid </Td> <Td> Ba (OH) </Td> <Td> − 944.7 </Td> </Tr> <Tr> <Td> Barium oxide </Td> <Td> Solid </Td> <Td> BaO </Td> <Td> − 548.1 </Td> </Tr>

The enthalpy of formation for a free element is