General Chemistry
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Find the fraction of volume occupied by atoms in a cubic close packed structure. Round off to four significant figures. The cubic close packed structure is the same as the face-centered cubic structure.
A hypothetical cobalt oxide has the formula CoxO, where x is (0.92 - 0.98). Think of this as a cobalt(II) oxide (CoO) with some Co sites vacant. The density of the oxide is 5.12 g/cm3. The oxide crystallizes in a face-centered cubic arrangement for oxygen atoms and the unit cell has an edge length of 454 pm. The Cobalt atoms in this oxide are either Co2+ or Co3+. What percent of the Co atoms in the oxide has an oxidation state of +3?
Specify the point and fractional coordinates for all of the zinc atoms in zinc fluoride. The unit cell of zinc fluoride is shown below. (Fractional coordinates use fractions to specify locations in the unit cell.)
Magnesium oxide follows the rock salt structure, and its unit cell has an edge length of 421 pm. Determine the length (in pm) of an Mg–O bond.
Magnesium oxide, MgO, follows the rock salt structure like that of NaCl. Determine the coordination number for the Mg2+ and O2– ions.
Zinc fluoride follows the crystal lattice shown below.
Determine the formula of zinc fluoride.
A sample of metal was determined to have a density of 8.96 g/cm3. The metal crystallizes in a face-centered cubic cell and using X-ray diffraction the edge length was measured to be 362 pm. Determine the atomic weight, atomic radius, and identity of the metal.
Platinum (Pt) has an atomic radius of 139 pm and a density of 21.4 g/cm3. What type of structure will Pt have?
The density of aluminum is 2.7 g/cm3 and it has an atomic radius of 143 pm. Aluminum will crystallize in what type of cubic unit cell?
An iron oxide follows the crystal lattice shown below.
Determine the formula for the iron oxide and the oxidation state of iron.
When lead crystallizes, it adopts a face-centered cubic crystal structure. The edge length of the unit cell is 495 pm. Calculate the radius (in pm) and density (in g/cm3) of a lead atom.
At temperatures below 115 K, krypton forms a close-packed solid structure shown below.
Is the radius of krypton in the solid structure larger than its estimated bonding atomic radius?
Identify which unit cell below has the densest packing of atoms:
Gold crystallizes in a face-centered cubic arrangement with an edge length of 4.07 Å. Calculate the percentage of Au atoms that are on the surface of a 5.0 nm gold sphere. Use the surface area of a sphere of 4πr2, the volume of a sphere of 4/3πr3, and the diameter of a gold atom of 2.92 Å.
Gold crystallizes in a face-centered cubic arrangement with an edge length of 4.07 Å. Calculate the number of gold atoms on the surface of a 5.0 nm gold sphere. Use surface area of a sphere of 4πr2 and the diameter of a gold atom of 2.92 Å.
In a p-type semiconductor, the germanium is doped with elements that have an incomplete outer shell of electrons like aluminum, boron, and gallium.
The germanium cubic unit cell has 8 atoms per unit cell and an edge length of 5.65 Å. Calculate the mass of boron in mg if a 5 cm3 sample of the semiconductor is 2 ppm B.
Niobium has a higher atomic mass than copper but copper. However, copper has a higher density than niobium. Identify why copper is denser than niobium.
Greenockite (CdS) has a wurtzite structure with cell parameters: a = b = 4.271 Å, c = 6.969 Å. Another compound, cadmoselite (CdSe), also has wurtzite structure with cell parameters: a = b = 4.136 Å, c = 6.713 Å. Identify which of the two substances has a greater density given that a wurtzite structure has 2 formula units of the compound per unit cell.
Greenockite (CdS) has a wurtzite structure with cell parameters: a = b = 4.136 Å, c = 6.713 Å. Another compound, cadmoselite (CdSe), also has wurtzite structure with cell parameters: a = b = 4.271 Å, c = 6.969 Å. Why does cadmoselite have larger cell parameters than greenockite?
Identify the element and its atomic weight with a density of 10.49 g/cm3 and the edge of the unit cell is 4.08 Å. Assume the element crystallizes in a face-centered cubic lattice.
Which statement is true?
Given the representation for the cubic structure of K2O.
Calculate its density if its edge length is 643 pm.
Is the empirical formula for the given intermetallic compound Pt3Fe? How many of each type of atom is present in the unit cell?
There are three different types of crystal structures
Given the following ionic radii
Br- = 196 pm
Ag+ = 115 pm
Li+ = 0.76 pm
Cs+ = 167 pm
Determine the structure type of LiBr, CsBr, and AgBr
Barium titanate has a cubic unit cell. Determine its empirical formula if it is composed of Ba, O, and Ti
ZnS follows a zinc blende structure while FeO follows a rock salt structure. Using coordination numbers, explain why FeO has a higher melting point than ZnS.
Label each unit cells with the correct structure (rock salt structure, perovskite structure, zinc blende structure).
How many atoms are there in a face-centered cubic unit cell?
An unknown metal has a face-centered cubic structure. Its density and atomic radius are 8.96 g/cm3 and 0.1278 nm, respectively. Calculate the molar mass of the unknown metal.
Iridium follows a FCC structure and has a density of 22.4 g/cm3. Determine the radius of an Ir atom.
Determine the edge length and the density of silver given that it follows a face-centered cubic structure. The radius of a silver atom is 145 pm.
Magnesium sulfide has a face-centered cubic type lattice. In this structure, how many S2- are in contact with each Mg2+
A portion of the KBr lattice is shown below:
The density KBr is 2.75 g/cm³. Calculate the number of formula units of KBr contained in the cube shown. (Assume that the edge and corners of the cube are in the center of the atoms)
Calculate the length of the side of the cube based on the ionic radii of each element. The radius of K+ and Br- is 1.52 Å and 1.82Å respectively.
(Assume that the edge and corners of the cube are in the center of the atoms)
Arrange the crystal lattice structures in order of increasing packing efficiency.
i. Face-centered cubic
ii. Hexagonal close packed
iii. Body-centered cubic
iv. Simple-cubic
Nickel adopts a body-centered cubic unit cell with a density of 8.902 g/cm3
Identify each of the following:
i. the number of atoms per cm3
ii. the number of unit cells present per cm3
iii. the volume of a unit cell
iv. the edge length (Choose one below)
For the face-centered cubic unit cell, identify each of the following:
i. the number of corner atoms
ii. fraction of each corner atom in the cube
iii. number of body atoms
iv. fraction of each body atom in the cube
v. Total number of atoms inside the cube
Identify which of the following compounds cannot form a solid with a lattice-based like the KBr structure
Determine the actual number of atoms present inside the unit cell shown below.
Platinum crystallizes with the face-centered cubic unit cell. The radius of a platinum atom is 139 pm. Calculate the edge length of the unit cell and the density of platinum in g/cm3.