Distinguish between SEM and TEM. What is the principal difference in sample preparation and detection?
In: Chemistry
A 0.2054 g sample of CaCO3 (primary standard) is dissolved in hydrochloric acid and the solution is diluted with water to 250.0 mL (solution A). A 50.0 mL aliquot of solution A is titrated with 41.12 mL of EDTA solution. a) I calculated a Molarity of 0.00998. Is this correct? (show all calculation). b) Now a 100.0 mL sample of water containing Ca2+ and Mg2+ is titrated with 22.74 mL of the EDTA solution in the example above at pH = 10.00. Another 100 mL sample is treated with NaOH to precipitate Mg(OH)2, and then titrated at pH 13 with 15.86 mL of the same EDTA solution. Calculate the ppm of CaCo3 and MgCO3 in the sample.
In: Chemistry
When calcium carbonate is added to hydrochloric acid, calcium chloride, carbon dioxide, and water are produced.
CaCO 3 ( s ) + 2 HCl ( aq ) ⟶ CaCl 2 ( aq ) + H 2 O ( l ) + CO 2 ( g )
How many grams of calcium chloride will be produced when 31.0 g of calcium carbonate is combined with 12.0 g of hydrochloric acid?
Which reactant is in excess?
How many grams of the excess reactant will remain after the reaction is complete?
In: Chemistry
Part A
Zn(s)+Al3+(aq)?Zn2+(aq)+Al(s)
Express your answer as a chemical equation. Identify all of the phases in your answer.
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Part B
Cd(s)+Cu+(aq)?Cd2+(aq)+Cu(s)
Express your answer as a chemical equation. Identify all of the phases in your answer.
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Part C
I?(aq)+SO42?(aq)?H2SO3(aq)+I2(s)
Express your answer as a chemical equation. Identify all of the phases in your answer.
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In: Chemistry
(A) How many moles (of molecules or formula units) are in each sample? And please explain how the answer is found.
1) 20.0 g NO2
2) 1.35 kg CO2
3) 40.4 g KNO3
4) 102.3 kg Na2SO4
(B) How many molecules (or formula units) are in each sample? And please show how to find answer
1) 52.03 g CCl4
2) 73.85 kg NaHCO3
3) 123.22 g C4H10
4) 3.15×104 g Na3PO4
In: Chemistry
Electroanalysis
a) List four technique that can be applied to improve the speed,sensivity and detection limits of polarography?
b) Describe how an electrogravimetric analysis of a copper solution might be performed?
In: Chemistry
Explain why fluorescence is collected at an angle other than 180˚ to the excitation light, and why an emission filter is used.
In: Chemistry
Question
1. Describe four types of intermolecular interactions; sketch attractions between molecules (somehow communicate what the attraction is). Which of these is the strongest? Which is the weakest? What can a substance’s phase at room temperature tell us about the intermolecular interactions?
2. What types of substances can hydrogen bond? What is special about the hydrogen bond?
3. Define each of the following: vaporization; condensation; sublimation; deposition; melting (fusion); freezing. Which of these are exothermic? Which are endothermic?
4. Define the “heat of fusion” (ΔHfus) and “heat of vaporization” (ΔHvap). Why do these processes require an input of energy? What is the energy used for?
In: Chemistry
#1
Consider the iron sulfur rubredoxins having a single iron center in their natural biological environment. Which of the following statements is incorrect.
| The iron atom is usually found in a nearly tetrahedral geometry surrounded by sulfurs. |
| Iron(III) rubredoxins act as reducing agents during electron transfer reactions. |
| The iron(III) rubredoxins exhibit a larger paramagnetism than their corresponding iron (II) rubredoxins. |
| Rubredoxins are only capable of gaining or loosing a single electron. |
| Iron(II) and iron(III) rubredoxins are found as high-spin iron complexes. |
#2
Which of the following formal oxidation states are present under normal biological conditions for the most oxidized form of a Fe4S4 ferredoxin center?
| Fe(III)2Fe(II)2 |
| Fe(III)3Fe(II)1 |
| Fe(III)1Fe(II)3 |
| Fe(III)4 |
| Fe(II)4 |
In: Chemistry
Determine the concentration of a solution of ammonium chloride (NH4CL) that has pH of 5.17 at 25C.
In: Chemistry
Be sure to answer all parts.Calculate the percent ionization of benzoic acid for the following concentrations:
(a) 0.50 M, (b) 0.00050 M.
In: Chemistry
A 94.7-g sample of silver (s = 0.237 J/(g · °C)), initially at 348.25°C, is added to an insulated vessel containing 143.6 g of water (s = 4.18 J/(g · °C)), initially at 13.97°C. At equilibrium, the final temperature of the metal–water mixture is 22.63°C. How much heat was absorbed by the water? The heat capacity of the vessel is 0.244 kJ/°C.
In: Chemistry
4. Balance the following redox equations using the half reaction method under basic conditions:
a. H+ + Cu(s) + NO3 - → Cu2+ + NO2 + H2O
b. MnO4 - + Cl- + H+ → Mn2+ + Cl2 + H2O
c. Zn(s) + ClO3 - + H+ → Zn2+ + Cl- + H2O
d. Cl- + H+ + Cr2O7 2- → Cr3+ + Cl2 + H2O
e. Mn2+ + NaBiO3 + H+ → MnO4 - + Bi3+ + Na+ + H2O
In: Chemistry
A groundwater is being considered for use as a domestic supply. The water has a temperature of 15
In: Chemistry
What is the difference between a fixed-time enzyme assay and a kinetic enzyme assay and what are the units of enzyme activity?
In: Chemistry