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engineering
the science and engineering of materials

Questions and Answers of The Science And Engineering Of Materials

Explain the advantages and disadvantages of hydrogen as an alternative fuel.
Consider the following diagram when answering the questions below. a. Compare balls A and B in terms of potential energy in both the initial and final setups.b. Ball A has stopped moving in the
Calculate the kinetic energy of a baseball (mass = 5.25 oz) with a velocity of 1.0 × 102 mi/h.
It takes 585 J of energy to raise the temperature of 125.6 g mercury from 20.0οC to 53.5οC. Calculate the specific heat capacity and the molar heat capacity of mercury.
A 30.0-g sample of water at 280. K is mixed with 50.0 g water at 330. K. Calculate the final temperature of the mixture assuming no heat loss to the surroundings.
A 110.-g sample of copper (specific heat capacity = 0.20 J/οC ? g) is heated to 82.4οC and then placed in a container of water at 22.3οC. The final temperature of the water and copper is 24.9οC.
Given the following data calculate ΔH for the reaction Ca(s) + 2C(graphite) → CaCy(s) Ca(s) + {0,(g) → → CaO(s) CaO(s) + H,O(1) CH,(g) + ξO2(g) C(graphite) + 0,(g) ΔΗ = -62.8
In a coffee-cup calorimeter, 1.60 g NH4NO3 is mixed with 75.0 g water at an initial temperature of 25.00οC. After dissolution of the salt, the final temperature of the calorimeter contents is
Given the following data: Calculate the bond energy for the O2 bond, that is, calculate ΔH for: NO2(g) 203(8) NO(g) + O3(g) - NO(g) + O(g) 30₂(g) NO,(g) + O2(g) ΔΗ = 233 kJ ΔΗ =
Given the following data calculate ΔHο for the reaction Fe2O3(s) + 3CO(g) 3Fe,O,(s) + CO(g) → Fe3O4(s) + CO(g) 2Fe(s) + 3CO2(g) 2Fe,O4(s) + CO2(g) 3FeO(s) + CO2(g) ΔΗ° – ΔΗ° = ΔΗ°
Calculate ΔH for the reaction given the following data: N₂H4(1) + O₂(g) N₂(g) + 2H₂O(1)
A swimming pool, 10.0 m by 4.0 m, is filled with water to a depth of 3.0 m at a temperature of 20.2οC. How much energy is required to raise the temperature of the water to 24.6οC?
The preparation of NO2(g) from N2(g) and O2(g) is an endothermic reaction:The enthalpy change of reaction for the balanced equation (with lowest whole-number coefficients) is ΔH = 67.7 kJ. If 2.50
Four types of electromagnetic radiation (EMR) are ultraviolet, microwaves, gamma rays, and visible. All of these types of EMR can be characterized by wavelength, frequency, photon energy, and speed
What does it mean for something to have wavelike properties? Particulate properties? Electromagnetic radiation can be discussed in terms of both particles and waves. Explain the experimental
Defend and criticize Bohr’s model. Why was it reasonable that such a model was proposed, and what evidence was there that it “works”? Why do we no longer “believe” in it?
List the most important ideas of the quantum mechanical model of the atom. Include in your discussion the terms or names wave function, orbital, Heisenberg uncertainty principle, de Broglie,
Compare the first ionization energy of helium to its second ionization energy, remembering that both electrons come from the 1s orbital. Explain the difference without using actual numbers from the
Which has the larger second ionization energy, lithium or beryllium? Why?
Explain why a graph of ionization energy versus atomic number (across a row) is not linear. Where are the exceptions? Why are there exceptions?
Make sense of the fact that metals tend to lose electrons and nonmetals tend to gain electrons.
Explain electron from a quantum mechanical perspective, including a discussion of atomic radii, probabilities, and orbitals.
There are an infinite number of allowed electronic transitions in the hydrogen atom. Why don’t we see more lines in the hydrogen emission spectrum?
Explain what is meant by the term “excited state” as it applies to an electron. Is an electron in an excited state higher or lower in energy than an electron in the ground state? Is an electron
Consider the following statement: “The ionization energy for the potassium atom is negative, because when K loses an electron to become K+, it achieves a noble gas electron configuration.”
What is meant by an orbital?
How does probability fit into the description of the atom?
Is the following statement true or false? The hydrogen atom has a 3s orbital. Explain.
Prove mathematically that it is more energetically favorable for a fluorine atom to take an electron from a sodium atom than for a fluorine atom to take an electron from another fluorine atom.
What type of relationship (direct or inverse) exists between wavelength, frequency, and photon energy? What does a photon energy unit of a joule equal?
What do we mean by the frequency of electromagnetic radiation? Is the frequency the same as the speed of the electromagnetic radiation?
Describe briefly why the study of electromagnetic radiation has been important to our understanding of the arrangement of electrons in atoms.
The Bohr model only works for one electron species. Why do we discuss it in this text (what’s good about it)?
Which quantum number is related toa. The orientation of the orbital in space?b. The size of the orbital?c. The magnetic moment produced by an electrond. The shape of the orbital?
Many times the claim is made that subshells half-filled with electrons are particularly stable. Can you suggest a possible physical basis for this claim?
The changes in electron affinity as one goes down a group in the periodic table are not nearly as large as the variations in ionization energies. Why?
Scientists use emission spectra to confirm the presence of an element in materials of unknown composition. Why is this possible?
In the hydrogen atom, what is the physical significance of the state for which n = ∞ and E = 0?
Photosynthesis uses 660-nm light to convert CO2 and H2O into glucose and O2. Calculate the frequency of this light.
A photon of ultraviolet (UV) light possesses enough energy to mutate a strand of human DNA. What is the energy of a single UV photon and a mole of UV photons having a wavelength of 25 nm?
Octyl methoxycinnamate and oxybenzone are common ingredients in sunscreen applications. These compounds work by absorbing ultraviolet (UV) B light (wavelength 280–320 nm), the UV light most
It takes 7.21 × 10-19 J of energy to remove an electron from an iron atom. What is the maximum wavelength of light that can do this?
A particle has a velocity that is 90.% of the speed of light. If the wavelength of the particle is 1.5 × 10-15 m, calculate the mass of the particle.
Consider only the transitions involving the first four energy levels for a hydrogen atom: a. How many emissions are possible for an electron in the n = 4 level as it goes to the ground state?b.
In the 1930s, electron microscopes were first used to provide structural details of human cells. If an electron microscope uses electrons having a wavelength of 0.1 nm, calculate the velocity of the
Give the maximum number of electrons in an atom that can have these quantum numbers: a. n = 0, l= 0, me = b. n = 2, l = 1, me 3, ms = + 1/2 c. n = d. n = 2, l = 2 e. n = 1, l = 0, me = 0 0 -1,
In defining the sizes of orbitals, why must we use an arbitrary value, such as 90% of the probability of finding an electron in that region?
Draw atomic orbital diagrams representing the ground-state electron configuration for each of the following elements. a. Nab. Coc. KrHow many unpaired electrons are present in each element?
How many 4d electrons would be predicted in the ground state for the following elements?a. Zirconiumb. Cadmiumc. Iridiumd. Iron
Consider the following idealized PES spectrum for an element: What is the identity of the element? Relative number of electrons 1000 100 10 Energy (MJ/mol) 0.1
Consider the following idealized PES spectrum for carbon:Explain the location and relative intensities of the various peaks. Relative number of electrons 100 10 Energy (MJ/mol) 1 0.1
Consider the following idealized PES spectrum for potassium: Explain the location and relative intensities of the various peaks. Relative number of electrons 1000 100 10 Energy (MJ/mol) 0.1
Give a possible set of values of the four quantum numbers for all the electrons in a boron atom and a nitrogen atom if each is in the ground state.
The electron affinities of the elements from aluminum to chlorine are -44, -120, -74, -200.4, and -384.7 kJ/mol, respectively. Rationalize the trend in these values.
Order the atoms in each of the following sets from the least exothermic electron affinity to the most. a. N, O, Fb. Al, Si, P
Predict the atomic number of the next alkali metal after francium and give its ground-state electron configuration.
Lithium is often prescribed as a mood-stabilizing drug. Do you think the lithium prescribed is in the elemental form? What is the more likely form of the lithium to be prescribed as a drug?
Small daily doses of lithium carbonate taken orally are often given to treat manic-depressive psychoses. This dosage maintains the level of lithium ion in the blood at about 1 × 10–3 mol/L.a. What
Consider the following idealized PES spectrum for an element: What is the identity of the element? Explain the relative positions of the various peaks. Relative number of
The four most abundant elements by mass in the human body are oxygen, carbon, hydrogen, and nitrogen. These four elements make up about 96% of the human body. The next four most abundant elements are
We expect the atomic radius to increase going down a group in the periodic table. Can you suggest why the atomic radius of hafnium breaks this rule? (See data below.) Atomic Radii (in
Calculate, to four significant figures, the longest and shortest wavelengths of light emitted by electrons in the hydrogen atom that begin in the n = 5 state and then fall to states with smaller
Determine the maximum number of electrons that can have each of the following designations: 2f, 2dxy, 3p, 5dyz, and 4p.
Explain the electronegativity trends across a row and down a column of the periodic table. Compare these trends with those of ionization energies and atomic radii. How are they related?
The ionic compound AB is formed. The charges on the ions may be +1, -1; +2, -2; +3, -3; or even larger. What are the factors that determine the charge for an ion in an ionic compound?
Explain how bond energies can be used to estimate ΔH for a reaction. Why is this an estimate of ΔH? How do the product bond strengths compare to the reactant bond strengths for an exothermic
Give a rationale for the octet rule and the duet rule for H in terms of orbitals. Give the steps for drawing a Lewis structure for a molecule or ion. In general, molecules and ions always follow the
Consider the following statement: “Because oxygen wants to have a negative-two charge, the second electron affinity is more negative than the first.” Indicate everything that is correct in this
Define formal charge and explain how to calculate it. What is the purpose of the formal charge? Organic compounds are composed mostly of carbon and hydrogen, but also may have oxygen, nitrogen,
The following ions are best described with resonance structures. Draw the resonance structures, and using formal charge arguments, predict the best Lewis structure for each ion.a. NCO–b. CNO–
Explain the main postulate of the VSEPR model. List the five base geometries (along with bond angles) that most molecules or ions adopt to minimize electron-pair repulsions. Why are bond angles
Would you expect the electronegativity of titanium to be the same in the species Ti, Ti2+, Ti3+, and Ti4+? Explain.
The second electron affinity values for both oxygen and sulfur are unfavorable (endothermic). Explain.
What is meant by a chemical bond? Why do atoms form bonds with each other? Why do some elements exist as molecules in nature instead of as free atoms?
Why are some bonds ionic and some covalent?
How does a bond between Na and Cl differ from a bond between C and O? What about a bond between N and N?
Does a Lewis structure tell which electrons come from which atoms? Explain.
True or false? In general, a large atom has a smaller electronegativity. Explain.
What is the central idea of the VSEPR model?
Most atoms in nature are found bonded together to form compounds instead of existing as individual atoms. Why is this true?
Some of the important properties of ionic compounds are as follows: i. Low electrical conductivity as solids and high conductivity in solution or when moltenii. Relatively high melting and
Combustion reactions of fossil fuels provide most of the energy needs of the world. Why are combustion reactions of fossil fuels so exothermic?
Predict the type of bond (ionic, covalent, or polar covalent) one would expect to form between the following pairs of elements. a. Rb and Clb. S and S c. C and Fd. Ba and Se. N
The major industrial source of hydrogen gas is by the following reaction:Use bond energies to predict ΔH for this reaction. CH4(g) + H₂O(g) →→→ CO(g) + 3H₂(g)
Give the formula of a negative ion that would have the same number of electrons as each of the following positive ions. a. Na+b. Ca2+c. Al3+d. Rb+
Compare the electron affinity of fluorine to the ionization energy of sodium. Is the process of an electron being “pulled” from the sodium atom to the fluorine atom exothermic or endothermic? Why
Ampyra is a drug used to improve mobility in patients with multiple sclerosis (MS). The skeletal structure of Ampyra isDraw the Lewis structure (including resonance forms) for Ampyra.
One type of exception to the octet rule are compounds with central atoms having fewer than eight electrons around them. BeH2 and BH3 are examples of this type of exception. Draw the Lewis
Three resonance structures can be drawn for CO2. Which resonance structure is best from a formal charge standpoint?
Consider the molecular structures illustrated in the previous exercise. For each structure, give an example compound that has that arrangement of atoms.
Which of the molecules in Exercise 119 have net dipole moments (are polar)? Data in Exercise 119Predict the molecular structure (including bond angles) for each of the following.a. SeO3b. SeO2
Two different compounds exist having the formula N2F2. One compound is polar whereas the other is nonpolar. Draw Lewis structures for N2F2 consistent with these observations.
Calcium carbonate (CaCO3) shells are used by mollusks, corals, and snails to form protective coverings. Draw the Lewis structure for CaCO3. Be sure to include any resonance structures.
What do each of the following sets of compounds/ions have in common with each other? a. SO3, NO3-, CO32-b. O3, SO2, NO2-
Use bond energy values to estimate ΔH for the following gas phase reaction: C₂H₂(g) + H₂O₂(g) CH₂OHCH₂OH(g)
Look up the energies for the bonds in CO and N2. Although the bond in CO is stronger, CO is considerably more reactive than N2. Give a possible explanation.
The formulas of several chemical substances are given in the table below. For each substance in the table, give its chemical name and predict its molecular structure.
Which of the following compounds or ions exhibit resonance? a. O3b. CNO-c. AsI3d. CO32-e. AsF3
The compound NF3 is quite stable, but NCl3 is very unstable (NCl3 was first synthesized in 1811 by P. L. Dulong, who lost three fingers and an eye studying its properties). The compounds NBr3 and NI3
Identify the following elements based on their electron configurations and rank them in order of increasing electronegativity: [Ar]4s¹3d³; [Ne]3s²3p³; [Ar]4s²3d¹04p³; [Ne]3s²3p5.

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