Answer the following questions pertaining to the following equation. 4Ga + 3S2 -> 2Ga2S3

1. How many moles of Sulfur are needed to react with 12.5 moles of Gallium

2. How many moles of Sulfur are needed to react with 100.0 grams of Gallium?

3. How many grams of Gallium burned if 200.0 grams of aluminum oxide formed?

4. How many grams of Gallium Sulfide would form if 20.5 moles of Gallium burned?

Show your work!

1. How much energy is in a beta-Lyman emission of hydrogen?

2. The gamma Lyman emission of hydrogen corresponds to an electron dropping from which energy level to which other energy level?

A 20.00 mL solution of 0.200M diprotic acid (H2A, pK_a1=3.500, pK_a2=8.500) is titrated with 0.250M KOH. Sketch the titration curve for this titration. Label the x-axis, y-axis, pK_a's, and equivalence points.

Potentiometry is to be used to determine the concentration of a metal dication, M2+,
in water. The table below shows the dependence of the cell potential on [M2+]
(please note some data has been deliberately omitted).

Q 2(a)
With the aid of a graph, determine the Nernst slope and the Standard Cell Potential,
Eo’. Comment on the values obtained and state the number of electrons transferred.

Q 2(b)
Clearly explaining your reasoning, use the graph to estimate the potentials that are
missing in the table. Comment on the likely accuracy of your predictions.

Q 2(c)
The Standard Cell Potential for Cd2+/Cd is -0.43V, for Pb2+/Pb is -0.29 V and for
Cu2+/Cu is +0.34 V. Clearly explaining your reasoning, determine the likely identity
of the metal cation.

Q 2(d)
If the potential measured for an unknown solution is -0.318 V, determine the
concentration of M2+ in the sample.

Consider the decomposition of barium carbonate: BaCO3(s)???BaO(s)+CO2(g)

A) Calculate the equilibrium pressure of CO2 at 298 K.

B) Calculate the equilibrium pressure of CO2 at 1300K .

Pre-lab questions:

Q 1. Based on the Three Source of Error

Three sources of error in acid-base titration

1. We notice the colour change of the solution due to presence of indicator at the end point (one extra drop from buret added to solution in conical flask after equivalence point) and not at the equivalence point (when a number of moles of acid=number of moles of base).

2. Parallax error: When we take the reading of solution in the buret from an angle rather than looking straight at the lower meniscus in colorless solutions and upper meniscus in colored solutions, this gives an error in the final calculation of the molarity of our acid.

3. The precision of the buret: Some burets may be less precise than others in giving the correct reading. This increases the uncertainty in the measurement of the volume of titrant used.

a) Give specific ways that you might avoid each one

b) During titration of an acid with a base, the sides of the Erlenmeyer flask are washed with distilled water. Do you think this rinsing will affect the outcome of the titration? Why or why not?

A) For the gas phase decomposition of hydrogen iodide at 700 K 2 HIH2 + I2 the average rate of disappearance of HI over the time period from t = 0 s to t = 1446 s is found to be 5.67×10-4 M s-1. The average rate of formation of H2 over the same time period is M s-1.

B) The rearrangement of cyclopropane to propene at 500 °C (CH2)3CH3CH=CH2 is first order in (CH2)3 with a rate constant of 6.70×10-4 s-1. If the initial concentration of (CH2)3 is 6.00×10-2 M, the concentration of (CH2)3 will be 1.06×10-2 M after s have passed.

C) The activation energy for the gas phase decomposition of ethyl chloroformate is 123 kJ. ClCOOC2H5C2H5Cl + CO2 The rate constant at 450 K is 2.62×10-4 /s. The rate constant will be 2.86×10-3 /s at K.

balance each equation.

Mg(s)+HBr(aq) ------ MgBr2(s) + H2(g)

B. CO(g) + O2(g) ----------CO2 (g)

c. PbS (s) + O2 (g) ---------PbO (s) + SO2(g)

d.H2SO4 +NAOH -------- Na2SO4 +H2O

e. H3PO4 +Ca (OH)2--------CA3 (PO4)2+ H2O

Consider the combustion of propane gas, C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l) Ho = -2,220 kJ/mol Propane (just C3H8) is often used for gas grills. Anyone who has every filled or moved those tanks knows they can get pretty heavy. a) How many grams of propane are in 1 pounds of propane? Use the conversion 1 lb = 454 g. (Express your answers for the next three questions in scientific notation. For example use 2.3e-5 to indicate a number such as 2.3 x 10-5.) grams b) How many moles of propane are in 1 pounds of propane? moles c)How much heat can be obtained by burning 1 pounds of propane? (Remember to look at this from the viewpoint of the surroundings, since the question asks how much heat can be OBTAINED.) kJ What is the enthalpy change for 12 CO2(g) + 16 H2O(l) 4 C3H8(g) + 20 O2(g) (Hint: compare this equation to the combustion equation for propane.

_kJ

Kp for the equilibrium N2(g)+ 3H2(g) <> 2NH3(g) is 4.51 x 10^-5 at 450C. For each of the mixtures listed here, indicated whether the mixture is at equilbrium at 450C. If it is not at equilibrium , indicate the direction in which the mixture must shift to achieve equilibrium.

a) 98 atm NH3, 45 atm N2, 55atm H2

b) 57 atm NH3 143 atm N2, no H2

c)13 atm NH3, 27 atm N2, 82 atm H2

Calculate the mass percent of a NaCl solution in which 141 g of NaCl is dissolved in 4.00 L of water at 25 ∘C (density = 0.997 g/mL).

Express your answer numerically.

The He⁺ ion contains only one electron and is therefore a hydrogen-like ion. Calculate the wavelengths of the first four transitions in the Balmer series of the He⁺ ion. List your answers in increasing transition order by entering the wavelength that corresponds to the first transition on the left. (The Rydberg constant for He is 4.39 × 10⁷ m⁻¹ and the Rydberg constant for H is 1.097 × 10⁷ m⁻¹)

Calculate these wavelengths for the same transitions in an H atom.

The pH of 0.1M NaCl is 7.14. After 1 drop of 0.1M HCl the pH change to 3.59. And after another 1 drop of 0.1M HCl the pH become 3.13.
Why does pH change significantly 7.14 to 3.59? And also why the pH doesn't change very much after another 1 drop of 0.1M HCl (3.59 to 3.13)?

Calculate the pH for each case in the titration of 50.0 mL of 0.110 M HClO(aq) with 0.110 M KOH(aq). Use the ionization constant for HClO.

What is the pH before addition of any KOH?

What is the pH after addition of 25.0 mL KOH?

What is the pH after addition of 40.0 mL KOH?

What is the pH after addition of 50.0 mL KOH

What is the pH after addition of 60.0 mL KOH?

hint: HClO is a weak acid with a Ka of 4.0×10−8. It reacts with strong base to produce Cl