Enthalpy change refers to the overall amount of heat added or lost with each step as you progress through your reaction.
The answer is C <span>The reactants lost internal energy.</span>
also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutron in the nucleus.
Answer : 6.41 moles of silicon are in the sample.
Solution : Given,
Moles of magnesium = 9.62 moles
The given chemical formula for talc is, 
From the given chemical formula we conclude that
The stoichiometry of magnesium and silicon is 3 : 2
3 moles of magnesium is equivalent to 2 moles of silicon
9.62 moles of magnesium will be equivalent to
moles of silicon
Therefore, the number of silicon present in sample are 6.41 moles.