Which molecule has 4 sigma (σ) bonds?

When the reaction: A + 2B → C was studied, the experimental data was obtained and plotted. Based on these graphs, what is the experimental rate law?  

How much heat is evolved or absorbed when 25.0 g of silver oxidizes to form silver oxide (Ag2O) under standard conditions? The enthalpy of formation (ΔHfo) of Ag2O is –31.05 kJ/mol and the molar mass of silver is 107.87 g/mol.

Which substance would have the smallest standard molar entropy?

For the reaction of hydrogen: H2(g) ⇌ 2H(g)    Kc = 1.1 Which reaction mixture(s) would proceed towards the products to reestablish equilibrium?  

What are two definitions of a base in an aqueous solution?

Which atom(s) in the acetic acid (CH3COOH, shown below) is/are sp3 hybridized as identified with the bolded/larger atom(s)?  

Which microscopic representation best represents a homogeneous mixture?

For the oxidation of iron to form iron(III) oxide: 4Fe(s) + 3O2(g) → 2Fe2O3(s) ΔSo = –549.73 J/K at 298 K The enthalpy of formation of Fe2O3(s) is –824.2 kJ/mol. What is the standard change in Gibbs free energy for this reaction at 298 K?  

For the reaction of: CH3NC(g) ⇌ CH3CN(g)   Kc = 11 What is the equilibrium concentration of CH3CN if the flask initially contains only 0.56 M CH3CN?