Determine the number of moles of H in each sample.

1). 8.48 mole NH3

2).0.111 mole N2H4

3). 36.0 mole C10 H22

1) 25.44 moles H

2) 0.444 moles H

3) 792 moles H

Explanation:

Step 1: Number of moles H in 8.48 moles NH3

In 1 mol NH3 we have 3 moles H

For 8.48 moles NH3 we have 3*8.48 = 25.44 moles H

Step 2: Number of moles H in 0.111  moles N2H4

For 1 mol N2H4 we have 4 moles H

For 0.111 moles N2H4 we have 4*0.111 = 0.444 moles H

Step 3: Number of moles H in 36.0 moles C1OH22

For 1 mol C10H22 we have 22 moles of H

For 36.0 moles C1OH22 we have 22*36.0 = 792 moles H

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.