Cobalt-60 has an atomic weight of 60.00 g/mol and a half-life of 5.260 years. If you start with a 1.000 gram sample of the
isotope, how much time will pass before you have just 0.100
grams of the isotope left?
a 16.44 years
b 18.44 years
C 17.47 years
d 14.77 years

im not exactly sure but i think its b!

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.