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chemistry for engineering students

Questions and Answers of Chemistry For Engineering Students

Which blocks of the periodic table comprise the main group elements?
Explain why the s block of the periodic table contains two columns, the p block contains six columns, and the d block contains ten columns.
The magnetic properties of atoms provide evidence that Hund’s rule leads to the correct electron configuration. Atoms that contain one or more unpaired electrons display a weak form of magnetism
The more unpaired electrons an element contains, the more strongly paramagnetic it will be. (See Problem 6.57.) Among the elements in the third row of the periodic table, which one should be the most
How does the effective nuclear charge help explain the trends in atomic size across a period of the periodic table?
Use the electron configurations of the alkali metals and your knowledge of orbitals and quantum numbers to explain the trend in atomic size of alkali metal atoms.
Using only a periodic table as a guide, arrange each of the following series of atoms in order of increasing size. (a) Na, Be, Li,(b) P, N, F, (c) I, O, Sn
At which ionization for chlorine would you expect the first large jump in ionization energy? Would this be the only large jump in energy if you continued to ionize the chlorine?
How do we explain the fact that the ionization energy of oxygen is less than that of nitrogen?
Which element would you expect to have the largest second ionization energy, Na, C, or F? Why?
Indicate which species in each pair has the more favorable (more negative) electron affinity. Explain your answers.(a) Cl or S, (b) S or P, (c) Br or As
Rank the following in order of decreasing ionization energy: Cl, F, Ne+, S, S_.
LED bulbs offer a fairly new lighting alternative, and are becoming increasingly popular in home lighting. These bulbs combine excellent energy efficiency with the “warm” light and dimming
Several excited states of the neon atom are important in the operation of a helium-neon laser. In these excited states, one electron of the neon atom is promoted from the 2p level to a higher energy
How much energy could be saved each year by replacing incandescent bulbs with LED bulbs? Assume that six 60-watt lamps are lit an average of three hours a night and they are each replaced with 8-watt
Which of the waves depicted here has the highest frequency? Explain your answer. Ь с
What is the relationship between the number of photons and the intensity of light?
What is the difference between continuous and discrete spectra?
The p and d orbitals are sometimes referred to as directional. Contrast them with s orbitals to offer an explanation for this terminology.
Why does the size of an orbital have an effect on its energy?
How does the charge of electrons provide some rationale for Hund’s rule?
Describe how valence electron configurations account for some of the similarities in chemical properties among elements in a group.
Why is there no element to the immediate right of magnesium in the periodic table?
The graph below shows the first three ionization energies for sodium, magnesium, and aluminum. Without consulting a list of values, determine which line in the graph corresponds to each element.
A particular element has the following values for its first four ionization energies: 900, 1760, 14,850, and 21,000 kJ/mol. Without consulting a list of ionization energy values, determine what group
Which graph correctly depicts the first ionization energy of three elements in groups 14 (dashed line) and 17 (solid line)? Explain the reasoning you used to make your choice. 1st I.E. Si Br Ge 1st
The visible lines in the hydrogen atom emission spectrum arise from transitions with a final state with n = 2. In what spectral region should we expect to find transitions that have a final state of
An excited He+ ion returns to the ground state by emitting a series of three photons, with wavelengths of 26 nm, 469 nm, and 1014 nm. The process is represented in the energy level diagram below.
Why do valence electrons experience a smaller effective nuclear charge rather than the full charge of the nucleus?
Why does the existence of line spectra imply that electrons occupy quantized energy levels in atoms?
The Rb+ ion happens, by coincidence, to be roughly the same size as the Cl- ion. What does this fact mean must be true about the relative sizes of the Rb and Cl atoms?
How does the screening by core electrons compare with the screening by valence electrons in an atom?
What is the only noble gas that does not have a ns2np6 electron configuration? How can it be a noble gas without this electron configuration?
The photoelectric effect can be used to measure the value of Planck’s constant. Suppose that a photoelectric effect experiment was carried out using light with ν = 7.50 × 1014 s-1 and ejected
A mercury atom is initially in its lowest possible (or ground state) energy level. The atom absorbs a photon with a wavelength of 185 nm and then emits a photon with a frequency of 4.924 × 1014 Hz.
A metallic sample is known to be barium, cesium, lithium, or silver. The electron binding energies for these metals are listed in the following table:One way to identify the element might be through
When a photoelectric effect experiment was carried out using a metal “M” and light at wavelength λ1, electrons with a kinetic energy of 1.6 × 10-19 J were emitted. The wavelength was reduced to
When a helium atom absorbs light at 58.44 nm, an electron is promoted from the 1s orbital to a 2p orbital. Given that the ionization energy of (ground state) helium is 2372 kJ/mol, find the longest
Arrange the members of each of the following sets of cations in order of increasing ionic radii. (a) K+, Ca2+, Ga3+, (b) Ca2+, Be2+, Ba2+, Mg2+,(c) Al3+, Sr2+, Rb+, Na+,(d) K+, Ca2+, Rb+
Arrange the following sets of anions in order of increasing ionic radii. (a) Cl-, S2-, P3-,(b) O2-, S2-, Se2-,(c) N3- ,S2-, Br-, P3-, (d) Cl-, Br-, I-
The photoelectric effect can be used in engineering designs for practical applications. For example, infrared goggles used in night-vision applications have materials that give an electrical signal
Some spacecraft use ion propulsion engines. These engines create thrust by ionizing atoms and then accelerating and expelling them. According to Newton’s laws, this leads to thrust in the opposite
Ionization gauges for pressure measurement (see Section 5.7) can be manipulated by changing the voltage of the electron collection grid (see Figure 5.11). Referring to Table 6.5, if the voltage is
Laser welding is a technique in which a tightly focused laser beam is used to deposit enough energy to weld metal parts together. Because the entire process can be automated, it is commonly used in
Atomic absorption spectroscopy is based on the atomic spectra of the elements being studied. It can be used to determine the impurities in a metal sample. If an element is present, light at the
The red color in fireworks is the result of having strontium- containing salts in the fireworks bomb. Similarly, the green/blue colors sometimes seen in fireworks arise from copper salts. Based on
When we say that the existence of atomic spectra tells us that atoms have specific energy levels, are we using deductive or inductive reasoning?
When Bohr devised his model for the atom, was he using deductive or inductive reasoning? Explain your answer.
The photochemical reaction that initiates the production of smog involves the decomposition of NO molecules, and the energy needed to break the N—O bond is 1.04 × 10-18j.(a) What is the longest
Define the term refraction.
Consider the experimental apparatus shown in the photo to the left, in which a candle is suspended above boiling water. This equipment could be used to test a hypothesis about the chemical
Chlorofluorocarbons were used for many years as refrigerants. One such molecule, C2Cl2F2, is synthesized from the reaction of CCl4 with HF. Suppose that you have 150 tons of carbon tetrachloride as a
When heated in air, some element, X, reacts with oxygen to form an oxide with the chemical formula X2O3. If a 0.5386-g sample of this unknown element yields an oxide with a mass of 0.7111 g, describe
Bismuth selenide, Bi2Se3, is used in semiconductor research. It can be prepared directly from its elements by the reaction, 2 Bi + 3 Se → Bi2Se3. Suppose that you need 5 kg of bismuth selenide for
The best way to generate small amounts of oxygen gas in a laboratory setting is by decomposing potassium permanganate:Suppose that you are testing a new fuel for automobiles, and you want to generate
An ore sample with a mass of 670 kg contains 27.7% magnesium carbonate, MgCO3. If all of the magnesium carbonate in this ore sample is decomposed to form carbon dioxide, describe how to determine
Existing stockpiles of the refrigerant Freon-12, CF2Cl2, must be destroyed under the terms of the Montreal Protocol because of their potential for harming the ozone layer. One method for doing this
Elemental analysis is sometimes carried out by combustion of the sample. For a hydrocarbon, the only products formed are CO2 and H2O. If a 1.36-g sample of an unknown hydrocarbon is burned and 2.21 g
Write the balanced chemical equation for the combustion of ethane, C2H6, and answer these questions.(a) How many molecules of oxygen would combine with 14 molecules of ethane in this reaction? (b)
Aluminum metal reacts with sulfuric acid to form hydrogen gas and aluminum sulfate.(a) Write a balanced chemical equation for this reaction. (b) Suppose that a 0.792-g sample of aluminum that
A metallurgical firm wishes to dispose of 1300 gallons of waste sulfuric acid whose molarity is 1.37 M. Before disposal, it will be reacted with calcium hydroxide (slaked lime), which costs $0.23 per
When Al (OH)3 reacts with sulfuric acid, the following reaction occurs:If 1.7 ×103 g of Al (OH)3 is combined with 680 g of H2SO4, how much aluminum sulfate can form? 2 Al(OH)3 + 3 H₂SO4 →
Copper reacts with nitric acid via the following equation:What mass of NO(g) can be formed when 10.0 g of Cu reacts with 115 g of HNO3? 3 Cu(s) + 8 HNO3(aq) - 3 Cu(NO3)2(aq) + 2 NO(g) + 4H₂O(l)
How much HNO3 can be formed in the following reaction if 3.6 kg of NO2 gas is bubbled through 2.5 kg of water? 3 NO₂(g) + H₂O(l) → 2 HNO3(aq) + NO(g)
Hydrogen and oxygen are reacted, and the water formed is collected at 25°C, where it has a density of 0.997 g/mL. If 36.8 g of H2 and 168 g of O2 are reacted, how many mL of water will be collected?
Silicon carbide, an abrasive, is made by the reaction of silicon dioxide with graphite (solid carbon):We mix 150.0 g of SiO2 and 101.5 g of c. If the reaction proceeds as far as possible, which
Define the term theoretical yield.
What types of events happen in chemical reactions that lead to percentage yields of less than 100%?
Sometimes students in chemistry labs determine percentage yields greater than 100%. Assuming there is no calculation error, how could this happen?
Hydrazine, N2H4, is a weak base and can react with an acid such as sulfuric acid:What mass of hydrazine can react with 250. mL 0.225 M H2SO4? 2 N₂H4(aq) + H₂SO4(aq) → 2 N₂H₂ (aq) + SO4²(aq)
A metallurgical firm needs to dispose of 2.74 × 103 gallons of waste sulfuric acid whose concentration has been determined to be 1.53 M. Environmental regulations require them to neutralize the
Many mining operations produce tailings that can be oxidized to form acids, including sulfuric acid. One chemical that reacts in this way is chalcopyrite, CuFeS2, whose net oxidation can be described
Aluminum dissolves in HCl according to the equation written below, whereas copper does not react with HCl.A 35.0-g sample of a copper–aluminum alloy is dropped into 750 mL of 3.00 M HCl, and the
A student dissolves 17.3 g of a mixture of Na2O and BaO in water. To try to determine the amount of barium present, the student uses a volumetric pipette to add 10.00 mL of 0.550 M sulfuric acid,
Why are fuel additives used?
What is actually measured by the octane ratings of different grades of gasoline?
Offer an explanation as to how oxygenated fuels might increase the extent of combustion.
Aluminum hydroxide can be dissolved in hydrochloric acid to form aluminum chloride and water. Write a balanced chemical equation for this reaction. How many mL of 3.37 M HCl is needed to react with
What is the role of an indicator in a titration?
What volume, in milliliters, of 0.512 M NaOH is required to react completely with 25.0 mL 0.234 M H2SO4?
What is the molarity of a solution of nitric acid if 0.216 g of barium hydroxide is required to neutralize 20.00 mL of nitric acid?
Small quantities of hydrogen gas can be prepared by the following reaction:How many grams of H2 can be prepared from 25.0 mL of 6.00 M H2SO4 and excess zinc? Zn(s) + H₂SO4(aq) → ZnSO4(aq) +
Elemental phosphorous is used in the semiconductor industry. It can be obtained from an ore called fluoroapatite via reaction with SiO2 and C:Suppose a particular semiconductor production plant
Silicon carbide is an abrasive used in the manufacture of grinding wheels. A company is investigating whether they can be more efficient in the construction of such wheels by making their own SiC via
A mixture of 10.0 g of NO and 14.0 g of NO2 results in the production of 8.52 g of N2O3. What is the percentage yield? NO(g) + NO₂(g) → N₂O3(l)
Magnesium nitride forms in a side reaction when magnesium metal burns in air. This reaction may also be carried out in pure nitrogen.If 18.4 g of Mg3N2 forms from the reaction of 20.0 g of magnesium
The theoretical yield and the actual yield for various reactions are given below. Determine the corresponding percentage yields. Reaction 1 Reaction 2 Reaction 3 Reaction 4 Theoretical Yield 35.0
A reaction that produced 4.8 mg of taxol, an anticancer drug, is reported to have a yield of 38%. What was the theoretical yield?
Methanol, CH3OH, is used in racing cars because it is a clean-burning fuel. It can be made by this reaction:What is the percentage yield if 5.0 × 103 g H2 reacts with excess CO to form 3.5 × 104 g
When iron and steam react at high temperatures, the following reaction takes place:How much iron must react with excess steam to form 897 gof Fe3O4 if the reaction yield is 69%? 3 Fe(s) + 4H₂O(g)
The percentage yield of the following reaction is consistently 87%.How many grams of sulfur would be needed to obtain 80.0 g of CS2? CH4(g) + 4 S(g) → CS₂(g) + 2 H₂S(g)
Sulfur hexafluoride is a very stable gas useful in electrical generators and switches. It is formed by direct synthesis from the elements:If 92 g of SF6 is produced from the reaction of 115 g of
Industrial production of hydrogen gas uses the reaction shown below. If 1.00 metric ton of propane reacting with excess water yields 270 kg of H2, what is the percentage yield? C3H8(g) + 3 H₂O(l)
If 21 g of H2S is mixed with 38 g of O2 and 31 g of SO2 forms, what is the percentage yield? 2 H₂S + 3 O₂ → 2 SO₂ + 2 H₂O
Perform a web search to learn what restrictions (if any) on the use of MTBE in gasoline might exist in your local area.
Using the web, find information about the amount of lead in the environment during the past 50 years. Correlate what you observe with the presence or absence of tetraethyl lead in gasoline.
Using the web, find out how lead “poisons” the catalyst in a catalytic converter.
If 3.4 mol Al is mixed with 1.5 times as many moles of Fe2O3, what is the limiting reactant? 2 Al + Fe₂O3 → Al₂O3 + 2 Fe
If 8.4 moles of disilane, Si2H6, are combined with 3 times as many moles of O2, which is the limiting reactant? 2 Si₂H + 70₂4 SiO₂ + 6H₂O
The pictures below show a molecular-scale view of a chemical reaction between the compounds AB2 and B2. (Green balls represent B atoms and orange balls are A atoms). The box on the left represents

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