What is in 20Ca40.08 calcium in bohr model

The enthalpy of formation of water is -285.8 kj/mol. what can be inferred from this statement?

What type(s) of intermolecular forces are expected between ch3ch2cooh molecules? dipole forces, induced dipole forces, hydrogen bonding

Inside a flashbulb, oxygen surrounds a thin coil of magnesium. when the flashbulb is set off, a chemical reaction takes place in which magnesium combines with oxygen to form magnesium oxide. which of the chemical equations matches the reaction above? a. mg + o2 mgo2 + energy b. 2mg + o mg2o + energy c. 2mg + o2 2mgo + energy d. mg + o mgo + energy