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If 0.100 mol of solute is added to 0.500 L of solvent with a density of 0.790 g/mL, the molality of the solution is a. 0.166 m b. 0.253 m c. 1.27x10^-4 m d. none e. 0.200 m : b. This question counts the weight of two questions. The half-life of a reactant in a first-order reaction was measured to be 6.10 hours. If the starting concentration is 1.00 M, what is the remaining concentration after 7.43 hours? The first-order rate equations are ln [A]t = -kt + ln [A]0 and t1/2=0.693/k Calculate k, the rate constant and select the correct units for k (leave one extra significant figure to prevent rounding error). 2 | P a g e Calculate the remaining concentration after 7.43 hours. : k=0.01136 1/hr 0.430 M Adding 17.5 g of an unknown compound to 100.0 g of water results in a freezing point lowering of -1.80 °C. Calculate the molality and molar mass of the unknown compound. You may assume that the density of water is 1.00 g/mL, and Kf for water is 1.86 °C/m. Equation: ΔTf = Kf m : 0.9677m 1.81 g/mol Select the correct expression for the rate of the following reaction, in terms of the concentrations of reactants and products. 2 H2O2 → 2 H2O + O2 : rate= -1/2[H2O2]/d. t =1/2[h2o]/d.t =1/1[o2]/d. t the definition of molality (m) is a. mol solute per liter of solution b. none c. mol solute per liter of solvent 3 | P a g e d. mol solute per kilogram of solution e. mol solute per kilogram of solvent : e. the rate law for a second-order reaction is written : rate=k[A]^2 You would expect a molecule of the formula C8H18 to be most soluble in a. C6H6 b. none c. H2O d. CH3OH e. NH3 : a. gases are most soluble in water at a. high temps and low pressures b. high temps and high pressures c. low temps and low pressure