Chemistry Questions and Answers October 23, 2019

1. A 0.4723-g sample of primary-standard-grade Na 2 CO 3 required 34.78 mL of an H 2 SO 4 solution to reach the endpoint in the reaction: CO 3 2- (aq) + 2H + (aq) H 2 O(I) + CO 2 (g) What is the molar concentration of the H 2 SO 4 ? 2. Why is it not important that your titration flask be dry in order to standardize your KHP?

Identify which atomic orbitals are used to construct the specified sigma bonds:

la Bond a is spsp bond b is spsp bond c is spsp Identify which orbital is used to construct the nbond at the marked atom P

Acetic acid can also react as a very weak base pK b = 20. Two different sites on acetic acid might become protonated to give the conjugate acid. Draw both of these possible conjugate acids, and explain (resonance) why the correct one is more stable. Calculate the pK a of this conjugate acid.

After hot filtration removes insoluble impurities, the remaining solution is cooled in an ice bath without being disturbed. Explain what happens during the crystallization process and what happens if crystals form too quickly.

1. An aqueous solution consisting of 50 mg of butanoic acid 5 mL of water is to be extracted 3 times with 1.0 mL ether. If the distribution coefficient for this extraction is equal to 8.5, how much acid will remain in the aqueous layer after the three extraction? 2. In isolating the neutral component of your unknown, an ether solution of the

An equilibrium mixture of CO, O2 and CO2 at a certain temperature contains 0.0010 M CO2 and 0.0015 M O2. At this temperature, Kc equals 1.4 * 10 2 for the reaction. What is the equilibrium concentration of CO?

2CO (g)0 (g) 2CO2 (g) ,. 1.1 103 . 2.2 103 . 4.8 10 d. 6.6 x 10 MMM

An unspecified ratio of nitrogen gas and hydrogen gas are mixed in a container and then afterwards react to form ammonia. The initial mole fraction of nitrogen gas and the final mole fraction of nitrogen gas are the same. What was the initial mole fraction of hydrogen gas?

Arrange the steps for the synthesis of aspirin in sequential order. Every step should be used.

Begin experiment End experiment heat in a hot water bath add water and cool to room temperature observe crystal formation if necessary, chill and scratch sides of glass wash several times with water filter and collect pure product filter and collect crude product weigh out salicylic acid add concentrated phosphoric acid and acetic anhydride

Ammonia gas is condensed at its boiling point at 1.013 25

bar at 33.4C by the application of a pressure infinitesimally greater than 1 bar. To evaporate ammonia at its boiling point requires the absorption of 23.30 kJ mol1. Calculate (a) wrev per mole, (b) q per mole, (c) AU, and (d) AH.

At equilibrium, the concentrations in this system were found to be [N2]=[O2]=0.100 M and [NO]=0.400 M. N2(g) +O2(g) <------> 2NO(g) If more NO is added, bringing its concentration to 0.700 M, what will the final concentration of NO be after equilibrium is re-established? =______M

Calculate a lattice energy for CaH2(s) in kilojoules per mole using the following information: (a) Eea for H(g) = -72.8kj/mol. (b) Ei1 for Ca(g) = +589.8kJ/mol. (c) Ei2 for Ca(g) = +1154kJ/mol. Heat of sublimation for Ca(s) = +178.2kJ/mol. Bond dissociation energy for H2(g) = +435.9kJ/mol. Net energy change for the formation of CaH2(s) from the

Calculate the change in heat when 12.60g of water vapor (steam) at 100.0C condenses to liquid water and then cools to 22.50C. For water: Sice=2.09J/g*C DeltaHfus=6.01kJ/mol Swater=4.184J/g*C DeltaHvap=40.79kJ/mol Ssteam=1.99J/g*C

In a free radical polymerization of polystyrene, how can [I] and [M] be changed such that Rp is the same but DPn is reduced by a factor of 2?

A coffee-cup (constant pressure) calorimeter is used to carry out the following reaction in 269 mL of water (where X is a hypothetical metal): X + 2 H2O X(OH)2 + H2 In this process, the water temperature started at 25.0 C and increased as the reaction progressed. If 0.00777 mol of "X" was consumed during the reaction, and the rH of this reaction