At a certain temperature and pressure an element has the simple body-centred cubic unit cell, depicted below. The corresponding density is 8.597 g cm-3 and the atomic radius is 1.428 Å. Calculate (and enter) the atomic mass for this element (in amu).

Question 1

a)velocity of an electron emitted by a metal whose threshold frequency is 2.24×10¹⁴ s−1s−1 when it is exposed to visible light of wavelength 5.14×10⁻⁷ mm .

Find the Velocity

b)What is the de Broglie wavelength of an electron traveling at 1.61×10⁵ m/sm/s?

Find de Broglie wavelength

Methanoic acid has a Ka=1.6X10-4. Calculate the pH of the final solution when 23.90 mL of 0.100M NaOH is added to 25.00 mL of 0.100 M methanoic acid

calculate the pH at the equivalence point of a titration of 0.3326 g THAM pKa 5.92 dissolved initially in 25 mL of H2O with 0.1042 M Hcl please show step by step

Calculate the PH of the following solutions

a) 25g HCIO4 in 500ml aqueous solution

b) 0.2M hydrofluoric acid

c) 0.02M Ca(OH)2

d) 25g HCIO and 30g Ca(CIO)2 in 1000ml aqueous solution

For each process, state whether ΔG_sys, ΔH_sys, and ΔS_sys are positive, negative or zero.

a. An ideal gas is compressed in one step from 1 atm to 5 atm a constant temperature.

b. Water freezes at its normal freezing point.

c. Benzene dissolves in toluene.

12. Define terms system and surroundings. What does it mean to say a system and its surroundings are in thermal equilibrium?

What determines the directionality of energy transfer as heat?

8. Here we are going to consider the differences between spectra and chromatograms. A list is given below of characteristics and behaviors of UV spectra and liquid chromatography. Some characteristics listed apply only to spectra. Other characteristics apply only to chromatography. And here’s the tricky bit, some characteristics apply to both. From the list below enter each characteristic that is correct for that instrumental plot on the line associated with that instrumental plot. Be careful, think about your choices, misplaced characteristics are negative points.

1. Usually has molar absorptivity values reported in homogeneous liquid solution

2. In our work in this lab, the solvent system is the eluent

3. Spans the UV and visible regions of the electromagnetic spectrum

4. Can be used for analytical work

5. Displays radiation absorption by molecules in solution

6. Displays the retention/separation by an appropriate stationary phase of molecules in solution

7. Provides information about how molecules are distributed between mobile and stationary phases

8. Can be used to identify unknown components in samples

9. Has time as the independent variable on the detector output plot

10. Has wavelength as the independent variable on the detector output plot

11. Has absorbance as the dependent variable on the output plot

12. Is concerned with electronic transitions in molecules

13. Is concerned with molecular distribution between phases

14. May show the instrument output plot at a constant flow rate

A. Liquid Chromatography plot characteristics are: _______________

B. UV spectral plot characteristics are: ________________

2. For the diprotic weak acid H2A, Ka1 = 2.7 × 10-6 and Ka2 = 8.8 × 10-9. What is the pH of a 0.0500 M solution of H2A? What are the equilibrium concentrations of H2A and A2– in this solution?

The Ka of a monoprotic weak acid is 7.84 × 10-3. What is the percent ionization of a 0.149 M solution of this acid?

At 1 atm, how much energy is required to heat 55.0 g of H2O(s) at –22.0 °C to H2O(g) at 151.0 °C? Enthalpy of fusion 333.6 J/g 6010. J/mol Enthalpy of vaporization 2257 J/g
40660 J/mol Specific heat of solid H₂O (ice)
2.087 J/(g·°C) *
37.60 J/(mol·°C) *  Specific heat of liquid H₂O (water)
4.184 J/(g·°C) *
75.37 J/(mol·°C) *  Specific heat of gaseous H₂O (steam)
2.000 J/(g·°C) * 36.03 J/(mol·°C) *

A 280.0 mL buffer solution is 0.270 M in acetic acid and 0.270 M in sodium acetate.

What is the initial pH of this solution? Express your answer using two decimal places.

What is the pH after addition of 0.0150 mol of HCl? Express your answer using two decimal places.

What is the pH after addition of 0.0150 mol of NaOH?Express your answer using two decimal places.

The good chemist is tasket with determining the concentration of manganese for a water sample drawn from a well next to a mine. To analyze the sample using absorbance spectroscopy, she prepares six sample (0-5) by adding 10.00 mL well water to 50.00-mL volumetric flasks, then adding increasing volumes of 25.00 ppm maganese solution, and diluting the resulting solution to 50.00 mL with 0.1 M HNO3. Final analysis at lambda(max)= 280 nm produced a graph of absorbance vs ppm Mn with best-fit line y = 0.0428x + 0.0487.

a) What is the concentration in ppm of manganese in the well water sample?

b) A field method of analysis was developed for testing soil near the mine where a .570 g sample of soil is quickly dissolved in acid with an oxidizing agent and diluted to 100 mL.

i) While you wait for the extraction, you calivrate your USB-spectrometer with a 3.15x10^-4 M standard of MnO4- with an average absorbance of .407 at 565 nm in a 1 cm cuvette. A blank solution made from DI water and acid had an absorbance of .078. Find the molar absorptivity of permanganate complex

ii) A few mL of the unknown solution is placed in a 1 cm cell and the transmission is found to be 30% at 565 nm. Calculate the concentration of manganese in the extracted sample.

iii)What was the weight percent of manganese in the original soil sample. iv) Explain in one sentence why permanganate appears to be a purple color

A. The freezing point of water H₂O is 0.00°C at 1 atmosphere.

How many grams of iron(II) nitrate (179.9 g/mol), must be dissolved in 228.0 grams of water to reduce the freezing point by 0.300°C ?

_____ g iron(II) nitrate.

B. The freezing point of water is 0.00°C at 1 atmosphere.

If 14.42 grams of ammonium acetate, (77.10 g/mol), are dissolved in 165.8 grams of water ...

The molality of the solution is _______ m.

The freezing point of the solution is _____°C.

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Calculate the equilibrium constant for the reaction
S₂O₈^2-(aq) + 2 Fe²⁺(aq) --> 2 Fe³⁺(aq) + 2 SO₄^2-(aq) at 25.0°C, given that the standard cells potentials for the two half reactions at this temperature are
S₂O₈^2-(aq) + 2 e^- 2 SO₄^2-(aq) E = +2.08 V
Fe³⁺(aq) + e^- Fe²⁺(aq) E = +0.77 V