Explore BrainMass

Explore BrainMass

    General Chemistry

    General Chemistry Problems

    5.38) Consider the following reaction: CH3OH (g) ---> CO (g) + 2 H2 (g) deltaH = +90.7 kJ a. Is heat absorbed or evolved in the course of this reaction? b. Calculate the amount of heat transferred when 45.0 g of CH3OH (g) is decomposed by this reaction at constant pressure. c. For a given sample of CH3OH, the enthalpy change

    Assorted General Chemistry Problems

    1.28) a. A cube of osmium metal 1.500cm on a side has a mass of 76.31g at 25°C. What is the density in g/cm3 at this temperature? b. The density of titanium metal is 4.51g/cm3 at 25°C. What mass of titanium displaces 65.8mL of water at 25°C? c. The density of benzene at 15°C is 0.8787g/mL. Calculate the mass of 0.1500L of be

    DeBroglie Equation Problems

    Calculate the mass for one photon of the following wavelengths of light: 1. red light with wavelength of 616 nm.........in kg 2. radio signal with frequency of 99.0 MHz........in kg 3. a photon of X-ray with energy of 2.30 x 10-15 J........in kg

    Calculate the deBroglie Wavelength

    Calculate the "deBroglie wavelength" for each of the following: 1. an electron moving at 0.82 times the speed of light...... in meters 2. a 125-g ball moving at a speed of 13.6 m/s.....in meters 3. a 61-kg person walking at a speed of 2.00 km/hr....in meters These answers explain why macroscopic (large) objects a

    Lyman Series for H

    The Lyman series in the hydrogen atom corresponds to transitions that originate from the n=1 level in absorption or that terminate in the n=1 level for emission. Calculate the energy, frequency (in inverse seconds and inverse centimeters), and wavelength of the least and most energetic transition in this series.

    Solving 7 Chemical Equations

    I desprately need help solving these chemical equations to help me to study for an exam. Rules for Solving Chemical Equations: 1. Write the chemical reaction in word form 2. Post your symbols 3. Post diatomics (for single units only) 4. Post oxidation numbers for compounds 5. Post subscription (for compounds onl

    Assorted General Chemistry Problems

    1) Given the following data table of average bond enthalpies, estimate the ΔH^rxn for the reactions 2H2+O2-- 2H2O Bond Average (kJ/mol) H-H 436 O=O 498 H-O 423 2) Draw eight distinct, valid Lewis resonance structures for the molecule XeO3. 3) Which structure or structures is or are mo

    Assorted General Chemistry Problems

    1) List the following gases in order of increasing root-mean-square speed, all at the same temperature: H2, He, O2, Ne 2) Under what conditions of pressure and temperature is a real gas most expected to deviate from ideal gas behaviour? 3) What intermolecular interactions would be the strongest between molecules CH2Cl2?

    Molecular Geometry and Bond Order Problems

    1) What is the molecular geometry of the ammonium ion? 2) What is the molecular geometry of the SO2Cl2 molecule? 3) What is the approximate F-S-F bond angle in sulfur hexafluoride? 4) What is the hybridization of the central atom in COCl2? 5) What is the hybridization of the central atom in selenium tetrabromide?

    Light and Quantum Numbers

    1) What is the molar concentration of a solution that is made by dissolving 6.30g of sodium chloride and diluting 1.00L?Report your answer to three significant figures. 2) In an experiment, 6.00g of Mg(s) was reacted completely with O2(g) to form MgO(s) and 148.5kJ of heat was evolved. What is the molar emthalpy of formation

    Assorted General Chemistry Problems

    1) In a combustion analysis, 2.00mg of vitamin C yielded 3.00mg CO2 and 0.816mg H2o. From mass spectrometry, it was found that the molecular weight of vitamin C is 176amu. Determine the mass composition of vitamin C, its empirical formula, and its molecular formula. 2) What is the energy of the photon that is emitted when the

    Time for Radio Signal to Travel from Saturn to Earth

    In June 2004, the Cassini-Huygens spacecraft began orbiting Saturn and transmitting images to Earth. The closest distance between Saturn and Earth is 746 million miles. What is the minimum amount of time it takes for the transmitted signals to travel from the spacecraft to Earth?

    Frequency and Wavelength

    Excited mercury atoms emit light strongly at a wavelength of 436 nm. What is the frequency of this radiation?

    Radius/Density From bcc and fcc Unit Cells

    Krypton crystallizes as a fcc (face centered cubic unit cell) having an edge length of 559 pm. (a.)What is the density of solid Krypton? (b.) What is the atomic radius of a krypton atom? (c.)What is the volume of one krypton atom? Potassium crystallizes in a bcc (body centered cubic unit cell) structure. The atomic radi

    Fission and isotopes

    1a.) You have 16 electrons, 16 protons, and 16 neutrons. You can combine them to make 8 Helium (He-4) atoms, 4 beryllium atoms (Be-8), 2 oxygen atoms (O-16), or one sulfur atom (S-32). What will you do to make the most stable product? Info: H-1 1.00782505 amu He-4 4.0026033 amu Be-8 8.0053052 amu O-16

    solubility of PbBr2 in various solutions

    If the solubility product of PbBr2 is 8.9 x 10^(-6). What is the molar solubility: (A) in pure water? (B) in 0.12 Molar KBr solution (C) in 0.18 Molar Pb(NO3)2 solution

    Isotope GA-67

    1. The isotope GA-67 is used medically to scan for various tumors. a.) Write the nuclear symbol for Ga-67 b.) How many protons are there in the nucleus? c.) How many neutrons are there? d.) Calculate ΔE in kJ when 1.00 of Ga-71 (nuclear mass of 70.9476 amu) is bombarded by an α-particle producing As-72 (nuclear mas

    Chemistry Expressions

    1. (a) Express 50 days in seconds (b) Convert 3.75 meter/sec to km/hr. Express the results in scientific notation. 2. Perform the following operations and express the answer with the appropriate number of significant figures. 863[1255-(3.45*10.8)] 3. The recommended dose of Elexophyllin (a drug used to treat


    A gas sample containing N2 and O2 was found to contain 72% N2. If the pressure of the sample was 2.0 atm, what is the partial pressure of O2? A. 0.56 ATM B. 0.28 ATM C. 1.44 ATM D. O.72 ATM E. 0.43 ATM

    [Pb 2+] and [I-]

    If a small sample of pure PbI2 is shaken with water to produce a saturated solution, What must be the relationship between [Pb 2+] and [I-] in that solution? Refer to equation below. PbI2 (s) <--> Pb^ 2+ (aq) + 2I (aq)


    The pascal is the SI unit for pressure defined as force (in newtons) per unit area ( in m2). If the force exerted by a gas on a 2.5 square meter area is 8.5 newtons, what is the pressure of the gas in Pa? A. 0.29 B. 0.21 C. 8.5 D. 17 E. 3.4

    Value of Kb

    The [OH-] = 1.3 x 10^ -6 M for a 0.025 M solution of a weak base. Calculate the value of Kb for this weak base. a) 5.2 x 10 ^ -5 b) 3.1 x 10 ^ -7 c) 7.7 x 10 ^ -9 d) 4.0 x 10 ^ -8 e) 6.8 x 10 ^ -11.

    Packing of Particles in Solids-space Lattices

    Hexagonal Closet Packaging vs. Cubic Closet Packaging (face-centered) vs. Body-centered a) Which of the three types of packaging has the least efficient arrangement of atoms? Justify the answer. b) How do the two more efficient forms of packing compare regarding volume? c) What is the relationship between coordination n

    Chemical Bonding: Melting Point

    1. Consider the following data: expect a BeF2 molecule to be linear but an SF2 molecule to be angular. Solubility in Water Melting (kg/kg H2O, 25oC) Point (oC) NaF 0.042 988 NaCl 0.357 801 NaBr 1.16 755 Nai 1.84 651 a) Explain the decreasing melting point from NaF to Nai. b) Explain th

    Chemical Bonding

    1. Consider you would expect a BeF2 molecule to be linear but an SF2 molecule to be angular. 2. a) How would you designate the hybrid orbitals formed by "mixing" one d one s and two p orbitals? b) How many of the hybrid orbitals would be formed by the mixing? 3. Explain why C20H40 is a solid at 25oC, while C4H8 is a gas