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chemical engineering

Questions and Answers of Chemical Engineering

Cobalt-60 is a strong gamma emitter that has a half-life of 5.26 yr. The cobalt-60 in a radiotherapy unit must be replaced when its radioactivity falls to 75% of the original sample. If an original
How much time is required for a 6.25-mg sample of 51Cr to decay to 0.75 mg if it has a half-life of 27.8 days?
Radium-226, which undergoes alpha decay, has a half-life of 1600 yr. (a) How many alpha particles are emitted in 5.0 min by a 10.0-mg sample of 226Ra? (b) What is the activity of the sample in mCi?
Cobalt-60, which undergoes beta decay, has a half-life of 5.26 yr. (a) How many beta particles are emitted in 600 s by a 3.75-mg sample of 60Co? (b) What is the activity of the sample in Bq?
The cloth shroud from around a mummy is found to have a 14C activity of 9.7 disintegrations per minute per gram of carbon as compared with living organisms that undergo 16.3 disintegrations per
(a) What is the half-life of the decay?(b) What is the rate constant for the decay?
A wooden artifact from a Chinese temple has a 14C activity of 38.0 counts per minute as compared with an activity of 58.2 counts per minute for a standard of zero age. From the half-life for 14C
Potassium-40 decays to argon-40 with a half-life of 1.27 × 109 yr. What is the age of a rock in which the mass ratio of 40Ar to 40K is 4.2?
The half-life for the process is 238U → 206Pb is 4.5 × 109 yr. A mineral sample contains 75.0 mg of and 18.0 mg of 206Pb.What is the age of the mineral?
The thermite reaction, Fe2O3(s) + 2 Al(s) → 2 Fe(s) + Al2O3(s), ΔH° = - 851.5 kJ/mol is one of the most exothermic reactions known. Because the heat released is sufficient to melt the iron
How much energy must be supplied to break a single aluminum-27 nucleus into separated protons and neutrons if an aluminum-27 atom has a mass of 26.9815386 amu? How much energy is required for 100.0
How much energy must be supplied to break a single 21Ne nucleus into separated protons and neutrons if the nucleus has a mass of 20.98846 amu? What is the nuclear binding energy for 1 mol of 21Ne?
The atomic masses of hydrogen-2 (deuterium), helium-4, and lithium-6 are 2.014102 amu, 4.002602 amu, and 6.0151228 amu, respectively. For each isotope, calculate (a) The nuclear mass (b) The nuclear
The atomic masses of nitrogen-14, titanium-48, and xenon- 129 are 13.999234 amu, 47.935878 amu, and 128.904779 amu, respectively. For each isotope, calculate (a) The nuclear mass (b) The nuclear
The energy from solar radiation falling on Earth is1.07 Ã— 1016 kJ/min.(a) How much loss of mass from the Sun occurs in one day from just the energy falling on Earth?(b) If the energy
All the stable isotopes of boron, carbon, nitrogen, oxygen, and fluorine are shown in the chart in the right hand column (in red), along with their radioactive isotopes with t1/2 > 1 min (in
Based on the following atomic mass values- 1H, 1.00782 amu; 2H, 2.01410 amu; 3H, 3.01605 amu; 3He, 3.01603 amu; 4He, 4.00260 amu-and the mass of the neutron given in the text, calculate the energy
Which of the following nuclei is likely to have the largest mass defect per nucleon:(a) 59Co(b) 11B(c) 118Sn(d) 243Cm?Explain your answer.
The isotope has the largest binding energy per nucleon of any isotope. Calculate this value from the atomic mass of nickel-62 (61.928345 amu) and compare it with the value given for iron-56 in Table
Iodine-131 is a convenient radioisotope to monitor thyroid activity in humans. It is a beta emitter with a half-life of 8.02 days. The thyroid is the only gland in the body that uses iodine. A person
Why is it important that radioisotopes used as diagnostic tools in nuclear medicine produce gamma radiation when they decay? Why are alpha emitters not used as diagnostic tools?
What is the function of the control rods in a nuclear reactor? What substances are used to construct control rods? Why are these substances chosen?
(a) What is the function of the moderator in a nuclear reactor? (b) What substance acts as the moderator in a pressurized water generator? (c) What other substances are used as a moderator in nuclear
The diagram shown here illustrates a fission process.(a) What is the unidentified product of the fission?(b) Use Figure 21.2 to predict whether the nuclear products of this fission reaction are
Complete and balance the nuclear equations for the following fission reactions:
A portion of the Sun's energy comes from the reactionwhich requires a temperature of 106 to 107 K.(a) Use the mass of the helium-4 nucleus given in Table 21.7 to determine how much energy is released
The spent fuel elements from a fission reactor are much more intensely radioactive than the original fuel elements. (a) What does this tell you about the products of the fission process in
Which type or types of nuclear reactors have these characteristics? (a) Does not use a secondary coolant (b) Creates more fissionable material than it consumes (c) Uses a gas, such as He or CO2, as
Which type or types of nuclear reactors have these characteristics? (a) Can use natural uranium as a fuel (b) Does not use a moderator (c) Can be refueled without shutting down
Hydroxyl radicals can pluck hydrogen atoms from molecules ("hydrogen abstraction"), and hydroxide ions can pluck protons from molecules ("deprotonation"). Write the reaction equations and Lewis dot
A laboratory rat is exposed to an alpha-radiation source whose activity is 14.3 mCi. (a) What is the activity of the radiation in disintegrations per second? In becquerels? (b) The rat has a mass of
A 65-kg person is accidentally exposed for 240 s to a 15-mCi source of beta radiation coming from a sample of 90Sr. (a) What is the activity of the radiation source in disintegrations per second? In
Radon-222 decays to a stable nucleus by a series of three alpha emissions and two beta emissions. What is the stable nucleus that is formed?
Indicate the number of protons and neutrons in the following nuclei:(b) 201Hg(c) potassium-39.
Equation 21.28 is the nuclear reaction responsible for much of the helium-4 production in our Sun. How much energy is released in this reaction?
Chlorine has two stable nuclides, 35CI and 37CI. In contrast, 36CI is a radioactive nuclide that decays by beta emission. (a) What is the product of decay of 36CI? (b) Based on the empirical rules
Nuclear scientists have synthesized approximately 1600 nuclei not known in nature. More might be discovered with heavyion bombardment using high-energy particle accelerators. Complete and balance the
The synthetic radioisotope technetium-99, which decays by beta emission, is the most widely used isotope in nuclear medicine. The following data were collected on a sample of 99Tc: Disintegrations
According to current regulations, the maximum permissible dose of strontium-90 in the body of an adult is 1 μCi (1 × 10-6 Ci). Using the relationship rate = kN, calculate the number of atoms of
Suppose you had a detection device that could count every decay event from a radioactive sample of plutonium-239 (t1/2 is 24,000 yr). How many counts per second would you obtain from a sample
Methyl acetate (CH3COOCH3) is formed by the reaction of acetic acid with methyl alcohol. If the methyl alcohol is labeled with oxygen-18, the oxygen-18 ends up in the methyl acetate:Do the C-OH bond
An experiment was designed to determine whether an aquatic plant absorbed iodide ion from water. Iodine-131 (t1/2 = 8.02 days) was added as a tracer, in the form of iodide ion, to a tank containing
The nuclear masses of 7Be, 9Be, and 10Be are 7.0147, 9.0100, and 10.0113 amu, respectively. Which of these nuclei has the largest binding energy per nucleon?
Indicate the number of protons and neutrons in the following nuclei:(b) 37CI (c) Thorium-232.
A 26.00-g sample of water containing tritium, emits 1.50 Ã— 103 beta particles per second. Tritium is a weak beta emitter with a half-life of 12.3 yr. What fraction of all the hydrogen in the
The Sun radiates energy into space at the rate of 3.9 × 1026 J/s. (a) Calculate the rate of mass loss from the Sun in kg/s. (b) How does this mass loss arise? (c) It is estimated that the Sun
The average energy released in the fission of a single uranium- 235 nucleus is about 3 × 10-11. If the conversion of this energy to electricity in a nuclear power plant is 40% efficient, what mass
Tests on human subjects in Boston in 1965 and 1966, following the era of atomic bomb testing, revealed average quantities of about 2 pCi of plutonium radioactivity in the average person. How many
A 53.8-mg sample of sodium perchlorate contains radioactive chlorine-36 (whose atomic mass is 36.0 amu). If 29.6% of the chlorine atoms in the sample are chlorine-36 and the remainder are naturally
Calculate the mass of octane, C8H18(l), that must be burned in air to evolve the same quantity of energy as produced by the fusion of 1.0 g of hydrogen in the following fusion reaction:Assume that
A sample of an alpha emitter having an activity of 0.18i is stored in a 25.0-mL sealed container at 22°C for 245 days. (a) How many alpha particles are formed during this time? (b) Assuming that
Charcoal samples from Stonehenge in England were burned in O2, and the resultant CO2 gas bubbled into a solution of Ca(OH)2 (limewater), resulting in the precipitation of CaCO3. The CaCO3 was removed
A 25.0-mL sample of 0.050 M barium nitrate solution was mixed with 25.0 mL of 0.050 M sodium sulfate solution labeled with radioactive sulfur-35. The activity of the initial sodium sulfate solution
Give the symbol for (a) a neutron, (b) an alpha particle, (c) gamma radiation.
(a) One of these structures is a stable compound; the other is not. Identify the stable compound, and explain why it is stable Explain why the other compound is not stable.(b) What is the geometry
(a) Draw the Lewis structures for at least four species that have the general formulawhere X and Y may be the same or different, and n may have a value from +1 to -2. (b) Which of the compounds is
Hydrazine has been employed as a reducing agent for metals. Using standard reduction potentials, predict whether the following metals can be reduced to the metallic state by hydrazine under standard
Both dimethylhydrazine, (CH3)2NNH2, and methylhydrazine, CH3NHNH2, have been used as rocket fuels. When dinitrogen tetroxide (N2O4) is used as the oxidizer, the products are H2O, CO2, and N2. If the
Carbon forms an unusual unstable oxide of formula C3O2, called carbon suboxide. Carbon suboxide is made by using P2O5 to dehydrate the dicarboxylic acid called malonic acid, which has the formula
Borazine, (BH)3(NH)3, is an analog of C6H6, benzene. It can be prepared from the reaction of diborane with ammonia, with hydrogen as another product; or from lithium borohydride and ammonium
Throughout history, arsenic(III) oxide, known simply to the general public as "arsenic," has been a poison favored by murderers: It is tasteless, colorless, can be easily added to food or drink,
Identify each of the following elements as a metal, nonmetal, or metalloid: (a) Phosphorus (b) Strontium (c) Manganese, (d) Selenium (e) Sodium (f) Krypton.
Consider the elements O, Ba, Co, Be, Br, and Se. From this list select the element that (a) Is most electronegative (b) Exhibits a maximum oxidation state of +7 (c) Loses an electron most readily (d)
Consider the elements Li, K, Cl, C, Ne, and Ar. From this list select the element that (a) Is most electronegative (b) Has the greatest metallic character (c) Most readily forms a positive ion (d)
Explain the following observations: (a) The highest fluoride compound formed by nitrogen is NF3, whereas phosphorus readily forms PF5. (b) Although CO is a well-known compound, SiO does not exist
Explain the following observations: (a) HNO3 is a stronger oxidizing agent than H3PO4. (b) Silicon can form an ion with six fluorine atoms, SiF62-, whereas carbon is able to bond to a maximum of
Complete and balance the following equations:(a) NaOCH3(s) + H2O(l) †’(b) CuO(s) + HNO3(aq) †’(d) NH2OH(l) + O2(g) †’ (e) Al4C3(s) + H2O(l) †’
Complete and balance the following equations:(a) Mg3N2(s) + H2O(l) †’(b) C3H7OH(l) + O2(g) †’(d) AlP(s) + H2O(l) †’ (e) Na2S(s) + HCl(aq) †’
(a) Give the names and chemical symbols for the three isotopes of hydrogen.(b) List the isotopes in order of decreasing natural abundance.(c) Which hydrogen isotope is radioactive?(d) Write the
(a) Identify the type of chemical reaction represented by the following diagram.(b) Place appropriate charges on the species on both sides of the equation.(c) Write the chemical equation for the
Are the physical properties of H2O different from D2O? Explain.
Give a reason why hydrogen might be placed along with the group 1A elements of the periodic table.
What does hydrogen have in common with the halogens? Explain.
Write a balanced equation for the preparation of H2 using (a) Mg and an acid (b) Carbon and steam (c) Methane and steam.
List (a) three commercial means of producing H2, (b) three industrial uses of H2.
Complete and balance the following equations:(a) NaH(s) + H2O(l) →(b) Fe(s) + H2SO4(aq) →(c) H2(g) + Br2(g) →(d) Na(l) + H2(g) →(e) PbO(s) + H2(g) →
Write balanced equations for each of the following reactions (some of these are analogous to reactions shown in the chapter). (a) Aluminum metal reacts with acids to form hydrogen gas. (b) Steam
Identify the following hydrides as ionic, metallic, or molecular: (a) BaH2 (b) H2Te (c) TiH1.7.
Describe two characteristics of hydrogen that are favorable for its use as a general energy source in vehicles.
Which of the following species (there may be more than one) is are likely to have the structure shown here:(a) XeF4(b) BrFe4+(c) SiF4(d) TeCI4(e) HClO4?(The colors do not reflect atom identities.)
The H2O2 fuel cell converts elemental hydrogen and oxygen into water, producing, theoretically, 1.23 V of energy. What is the most sustainable way to obtain hydrogen to run a large number of fuel
Why does xenon form stable compounds with fluorine, whereas argon does not?
A friend tells you that the "neon" in neon signs is a compound of neon and aluminum. Can your friend be correct? Explain.
Write the chemical formula for each of the following, and indicate the oxidation state of the halogen or noble-gas atom in each: (a) Calcium hypobromite (b) Bromic acid (c) Xenon trioxide (d)
Write the chemical formula for each of the following compounds, and indicate the oxidation state of the halogen or noble-gas atom in each: (a) Chlorate ion (b) Hydroiodic acid (c) Iodine
Name the following compounds and assign oxidation states to the halogens in them: (a) Fe(ClO3)3 (b) HClO2 (c) XeF6 (d) BrF5 (e) XeOF4 (f) HIO3.
Name the following compounds and assign oxidation states to the halogens in them: (a) KClO3 (b) Ca(IO3)2 (c) AlCl3 (d) HBrO3 (e) H5IO6 (f) XeF4.
Explain each of the following observations: (a) At room temperature I2 is a solid, Br2 is a liquid, and Cl2 and F2 are both gases.
Explain the following observations: Discuss.
Write balanced equations for each of the following reactions.(a) When mercury(II) oxide is heated, it decomposes to form O2 and mercury metal.(b) When copper(II) nitrate is heated strongly, it
You have two glass bottles, one containing oxygen and one filled with ozone. How could you determine which one is which?
Complete and balance the following equations: (a) CaO(s) + H2O(l) → (b) Al2O3(s) + H+(aq) → (c) Na2O2(s) + H2O(l) → (d) N2O3(g) + H2O(l) → (e) KO2(s) + H2O(l) → (f) NO(g) + O3(g) →
Predict whether each of the following oxides is acidic, basic, amphoteric, or neutral: (a) NO2 (b) CO2 (c) Al2O3 (d) CaO.
Select the more acidic member of each of the following pairs: (a) Mn2O7 and MnO2 (b) SnO and SnO2 (c) SO2 and SO3 (d) SiO2 and SO2 (e) Ga2O3 and In2O3 (f) SO2 and SeO2.
Write the chemical formula for each of the following compounds, and indicate the oxidation state of the group 6A element in each: (a) Selenous acid (b) Potassium hydrogen sulfite (c) Hydrogen
Write the chemical formula for each of the following compounds, and indicate the oxidation state of the group 6A element in each: (a) Sulfur tetrachloride (b) Selenium trioxide (c) Sodium
In aqueous solution, hydrogen sulfide reduces (a) Fe3+ to Fe2+ (b) Br2 to Br- (c) MNO4- to Mn2+ (d) HNO3 to NO2. In all cases, under appropriate conditions, the product is elemental sulfur. Write a
An aqueous solution of SO2 reduces (a) Aqueous KMnO4 to MnSO4(aq) (b) Acidic aqueous K2Cr2O7 to aqueous Cr3+ (c) Aqueous Hg2(NO3)2 to mercury metal. Write balanced equations for these reactions.
Write the Lewis structure for each of the following species, and indicate the structure of each: (a) SeO32- (b) S2Cl2; (c) Chlorosulfonic acid, HSO3Cl (chlorine is bonded to sulfur).
The SF5- ion is formed when SF4(g) reacts with fluoride salts containing large cations, such as CsF(s). Draw the Lewis structures for SF4 and SF5-, and predict the molecular structure of each.

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