Principles of chemistry: แบบฝึกหัด

Which process involves a substance losing energy and its particles moving closer together to form a regular, fixed arrangement?

What is the relative formula mass (\(M_r\)) of ammonium sulfate, \((NH_4)_2SO_4\)?
(\(A_r\) values: \(N = 14\), \(H = 1\), \(S = 32\), \(O = 16\))

Why does diamond have a significantly higher melting point than \(C_{60}\) fullerene, even though both are made of carbon atoms?

An atom of sodium has an atomic number of \(11\) and a mass number of \(23\). What is the total number of neutrons in the nucleus of this atom?

Which statement correctly explains why sodium chloride conducts electricity when molten but not when in the solid state?

Determine the number of protons and the number of electrons present in a sodium ion, \(Na^{+}\). (The atomic number of sodium is \(11\) and its mass number is \(23\)).

A sample of a copper oxide is reduced to its elements, producing \(1.27\text{ g}\) of copper and \(0.16\text{ g}\) of oxygen. Calculate the empirical formula of this copper oxide. (\(A_r\) values: \(Cu = 63.5, O = 16\))

An organic compound is found to contain \(80\%\) carbon and \(20\%\) hydrogen by mass. Given that its relative formula mass (\(M_r\)) is \(30\), determine the molecular formula of the compound. (\(A_r\) values: \(C = 12, H = 1\))

(a) Describe the arrangement and movement of particles in a liquid.
(b) State the name of the change of state when a liquid becomes a solid.
(c) Ammonia gas (\(NH_3\)) and hydrogen chloride gas (\(HCl\)) are released at opposite ends of a glass tube. They diffuse and react to form a white ring of ammonium chloride (\(NH_4Cl\)). Explain why the ring forms closer to the \(HCl\) end of the tube. (\(M_r\) of \(NH_3 = 17\), \(M_r\) of \(HCl = 36.5\))

An oxide of copper is analyzed and found to contain 12.7 g of copper and 1.6 g of oxygen.
(a) Determine the empirical formula of this oxide of copper.
(b) Write a balanced symbol equation for the reaction of copper with oxygen to form this specific oxide. Include state symbols.
(\(A_r\) values: \(Cu = 63.5\), \(O = 16\))