Which of the following is true for combustion reactions?

energy is absorbed.
energy is released.
hydrogen is a reactant.
nitrogen is a reactant.

Naoki's bicycle has a mass of 10 kg. if naoki sits on her bicycle and starts pedaling with a force of 168 n, causing an acceleration of 2.8 m/s2, what is naoki's mass?

In saturated organic compounds, all the bonds between carbon atoms are called?

How many grams of mgbr2 are needed to produce 75g or metal?