Question

11. Hassium (Hs, Z=108), discovered in 1984, is believed to be one of the most dense elements known. This is difficult to measure since it is highly radioactive. With an approximate MW=277 g/mol), and assuming it crystallizes in a face centered cubic structure, calculate its density. The edge length (a) of this cell is 0.4035 nm. 1 cm = 1 \times 10^{7} nm. (2 pts) Extra Credit Problem Both hydrazine and ammonia burn in oxygen to produce water and N$_2$ (g), with the balanced equations given below. \begin{itemize} \item What is the enthalpy per kilogram for each? (1 pt) \item On a mass basis (per kg) would hydrazine or ammonia be a better fuel? The molar mass of hydrazine is 32.0 g/mol, molar mass of ammonia is 17.0 g/mol. (1 pt) \end{itemize} N$_2$H$_4$ (l) + O$_2$ (g) $\longrightarrow$ 2 H$_2$O (l) + N$_2$ (g) $\Delta$H = -622.02 kJ 4 NH$_3$ (g) + 3O$_2$ (g) $\longrightarrow$ 6 H$_2$O (l) + 2 N$_2$ (g) $\Delta$H = -1529.6 kJ

          11. Hassium (Hs, Z=108), discovered in 1984, is believed to be one of the most dense elements known.
This is difficult to measure since it is highly radioactive. With an approximate MW=277 g/mol), and
assuming it crystallizes in a face centered cubic structure, calculate its density. The edge length (a) of
this cell is 0.4035 nm. 1 cm = 1 \times 10^{7} nm. (2 pts)
Extra Credit Problem
Both hydrazine and ammonia burn in oxygen to produce water and N$_2$ (g), with the balanced equations
given below.
\begin{itemize}
    \item What is the enthalpy per kilogram for each? (1 pt)
    \item On a mass basis (per kg) would hydrazine or ammonia be a better fuel? The molar mass of
    hydrazine is 32.0 g/mol, molar mass of ammonia is 17.0 g/mol. (1 pt)
\end{itemize}
N$_2$H$_4$ (l) + O$_2$ (g) $\longrightarrow$ 2 H$_2$O (l) + N$_2$ (g) $\Delta$H = -622.02 kJ
4 NH$_3$ (g) + 3O$_2$ (g) $\longrightarrow$ 6 H$_2$O (l) + 2 N$_2$ (g) $\Delta$H = -1529.6 kJ

11. Hassium (Hs, Z=108), discovered in 1984, is believed to be one of the most dense elements known.
This is difficult to measure since it is highly radioactive. With an approximate MW=277 g/mol), and
assuming it crystallizes in a face centered cubic structure, calculate its density. The edge length (a) of
this cell is 0.4035 nm. 1 cm = 1 ×10^7 nm. (2 pts)
Extra Credit Problem
Both hydrazine and ammonia burn in oxygen to produce water and N2 (g), with the balanced equations
given below.

* What is the enthalpy per kilogram for each? (1 pt)

* On a mass basis (per kg) would hydrazine or ammonia be a better fuel? The molar mass of
hydrazine is 32.0 g/mol, molar mass of ammonia is 17.0 g/mol. (1 pt)

N2H4 (l) + O2 (g) ⟶ 2 H2O (l) + N2 (g) ΔH = -622.02 kJ
4 NH3 (g) + 3O2 (g) ⟶ 6 H2O (l) + 2 N2 (g) ΔH = -1529.6 kJ

Added by Cesar A.

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