Which option is a compound? A. Oxygen B. Carbon dioxide C. Carbon D. Air

C. Carbon dioxide is a compound.

Its molecules consist of one carbon atom joined to two oxygen atoms. In the atmosphere, carbon dioxide is a greenhouse gas.

Sugar and water are chemically combined.(a solution is chemically combined while a mixture is mixed together without bonding the molecules)

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.