Given the following thermochemical equations:

X₂+3Y₂ equals 2XY₃ and Delta H =-340 kJ

X₂+2 Z₂ equals 2XZ₂ and Delta H = -170 kJ

2Y₂ + Z₂ equals 2Y₂Z and Delta H=-260kJ

Calculate the change in enthalpy for the following reaction

4XY3+7 Z₂ equals 6Y₂Z+4XZ₂

draw vsepr and valence bond picture for C2H2? label the bonds. for each sigma bond name the two orbitals that overlap to form it? for each pi bond name the two orbitals that overlap to form it. why are to pi ponds perpindicular to each other. why are quadruple bonds unlikely? Please label thank you.

A 0.4627 g sample of pewter, containing tin, lead, copper, and zinc, was dissolved in acid. Tin was precipitated as SnO2·4H2O and removed by filtration. The resulting filtrate and washings were diluted to a total volume of 200.0 mL. A 20.00 mL aliquot of this solution was buffered, and titration of the lead, copper, and zinc in solution required 34.11 mL of 0.001500 M EDTA. Thiosulfate was used to mask the copper in a second 25.00 mL aliquot. Titration of the lead and zinc in this aliquot required 34.45 mL of the EDTA solution. Finally, cyanide was used to mask the copper and the zinc in a third 30.00 mL aliquot. Titration of the lead in this aliquot required 24.39 mL of the EDTA solution. Determine the percent composition by mass of each metal in the pewter sample.

Complete the mechanism of the following Diels-Alder reaction by drawing the curved arrows for the concerted reaction and the final product formed.

A 0.8027 g sample of impure al2(CO3)3 decomposed with HCL: the liberated CO2 was collected on calcium oxide and found to weight 0.0507g calculate the percentage of aluminum in the sample

A solution of 0.172 M NaOH is used to neutralize 27.0 mL of a H2SO4 solution.

Part A

If 30.6 mL of the NaOH solution is required to reach the endpoint, what is the molarity of the H2SO4 solution?

H2SO4(aq)+2NaOH(aq)→2H2O(l)+Na2SO4(aq)

Express your answer with the appropriate units.

Enter your answer using dimensions of chemical concentration

You have 875 mL of an 0.39 M acetic acid solution. What volume (V) of 1.70 M NaOH solution must you add in order to prepare an acetate buffer of pH = 4.36? (The pKa of acetic acid is 4.76.)

(a) How many grams of CaCl2 are needed to make 250.9 g of a solution that is 30.5% (m/m) calcium chloride in water? Note that mass is not technically the same thing as weight, but (m/m) has the same meaning as (w/w).

-How many grams of water are needed to make this solution?

(b) What is the volume percent % (v/v) of an alcohol solution made by dissolving 117 mL of isopropyl alcohol in 747 mL of water? (Assume that volumes are additive.)

(c) The mass of solute per 100 mL of solution is abbreviated as % (m/v). (The abbreviation % (w/v) is also common.) How many grams of sucrose are needed to make 735 mL of a 34.0% (w/v) sucrose solution?

Consider the following reaction. 2NO2(g)⇌N2O4(g) When the system is at equilibrium, it contains NO2 at a pressure of 0.722 atm, and N2O4 at a pressure of 0.0521 atm. The volume of the container is then reduced to half its original volume. What is the pressure of each gas after equilibrium is reestablished?

PNO2= ?? atm

PN2O4= ?? atm

Part C

Go to the Phase Changes tab. Select the particular molecule, and set the temperature to the given values by using the stove to increase or decrease the temperature. Increase the pressure of the cylinder by moving the lid of the cylinder down with the help of the finger. The pressure of the cylinder is indicated by the pressure gauge on the top left corner of the simulation. On the right-hand side of the simulation is the phase diagram for the molecule.

As the molecules collide on the walls of the cylinder, the pressure of the cylinder does not remain constant; it fluctuates slightly as indicated by the gauge.

In the phase diagram, observe the red point. When a particular molecule is selected, set the temperature and pressure condition to the required value. Observe the position of the red point on the phase diagram when the pressure reaches approximately near the required value.

Which of the following conditions will result in the formation of a supercritical fluid?

Check all that apply.

What is the connection between the Pauli Exclusion principle, the Aufbau principle, the indeterminacy of fermions, electron configurations and quantum numbers. Why is shielding more effective for electrons in orbitals with lower principal quantum number than for electrons within the same shell?

Gas chromatography and the quantitative method of standard addition to constant volume were used to investigate the concentration of 2,4‑dichlorophenoxyacetic acid (a chlorinated phenoxy herbicide) in a water sample from Lake Eildon.

Liquid-liquid extraction using dichloromethane was used to extract 1.00 L of water sample and the combined extracts were made up to 25 mL in a volumetric flask. A 5.00 mL aliquot of the combined extract was added to each of two 10 mL volumetric flasks. To one flask was added 50.00 μL of a 1.150 x 10^-4 M standard solution of 2,4‑dichlorophenoxyacetic acid. Both flasks were then made up to the final volume. The GC analysis of 10.00 μL of injected sample from each flask resulted in peak areas of 245 mV.s and 290 mV.s for the signal in the chromatograms due to 2,4‑dichlorophenoxyacetic acid.

(Relative molar mass of 2,4-dichlorophenoxyacetic acid = 221.04 g.mol^-1)

(i). Calculate the concentration (mol/L) of 2,4-dichlorophenoxyacetic acid in the working standard solution used for quantitative analysis of the analyte

(ii). Write the standard addition equation and identify the terms to be applied

(iii). Apply the standard addition equation and determine the concentration in mg/L of 2,4‑dichlorophenoxyacetic acid in the original water sample from Lake Eildon

(iv). Identify the likely sources of experimental error in the laboratory method and calculate the percentage error in the value for the concentration of 2,4‑dichlorophenoxyacetic acid determined in (iii) (2 + 4 = 6 marks). Briefly, discuss how you would confirm the validity of the value determined in (iii)

(v). Discuss the likely health risks associated with a concentration of 30 μg/L of 2,4‑dichlorophenoxyacetic acid as compared to typical values found in Australian drinking waters

(vi) Discuss the effectiveness of dissolved oxygen to other common water treatment processes to effectively remove 2,4‑dichlorophenoxyacetic acid from Australian drinking waters

The substance HCO3-1 is amphiprotic, meaning is can act as either an acid or a base. Complete the reactions started below to show how it acts as an acid and as a base. Label the conjugate acid and base for each
reaction.

ACID REACTION: HCO3-1 + H2O(l) ?

BASE REACTION: HCO3-1 + H2O(l) ?

Hydrogen and methanol have both been proposed as alternatives to hydrocarbon fuels.

A) Write balanced reactions for the complete combustion of hydrogen.

B) Use standard enthalpies of formation to calculate the amount of heat released per kilogram of the fuel.

C) Write balanced reactions for the complete combustion of methanol.

D) Use standard enthalpies of formation to calculate the amount of heat released per kilogram of the fuel.

E) How does the energy of these fuels compare to that of octane (C8H18)? Amount of heat released by octane = ?.