If I remember correctly, the answer is <span>Friction force.</span>
So calculate the H for the other two reactions a room temperature and combine the reactions to calculate the H of the decomposition of calcium carbonate using the Hess's Law
It is A)The smallest unit of Ne
Hydrogen gas(H2) has a molar mass of 2 g. Molar mass of a substance is defined as the mass of 1 mole of that substance. And by 1 mole it is meant a collection of 6.022*10^23 particles of that substance.
So number of moles of H2 are 0.5 in this case. And thus it means there are (6.022*10^23)*0.5 particles( here they are molecules) in 1g of H2.
