Geochemistry

Question 1

Any change in one of the variables that determine the state of a system in equilibrium causes a shift in the position of equilibrium in a direction that tends to counteract the change in the variable under consideration.

Answer 1

Le Chatelier’s Principle

Question 2

“The branch of science that deals with energy levels and the transfer of energy between systems and between different states of matter”

Answer 2

Thermodynamics

Question 3

Refers to the energy content of a given system. The state is defined by specifying certain variables such as temperature, pressure, volume and composition.

Answer 3

State

Question 4

Father of geochemistry and largely known for his determination of the composition of the Earth’s crust.

Answer 4

Frank W. Clarke

Question 5

WMAP stands for

Answer 5

Wilkinson Microwave Anisotropy Probe

Question 6

What technique is often used to determine the chemical composition of a specific mineral.

Answer 6

EPMA (electron probe microanalyzer)

Question 7

First coined the term geochemistry in 1838.

Answer 7

Christian Friedrich Schonbein

Question 8

A maximum of 2 electrons can occupy an orbital and the 2 electrons must spin in the opposite directions

Answer 8

Pauli Exclusion Principle

Question 9

The ground state of an atom is found by filling the orbital from the lowest energy level upwards

Answer 9

Aufbau Principle

Question 10

Differentiate extensive and intrinsic state variables.

Answer 10

Extensive - Refers to state variables which are proportional to the quantity of matter (such as volume). Intrinsic - variables which are independent of quantity, that instead describe the whole system (such as density, temperature, and concentration).

Question 11

Enumerate and explain the two different processes the way a system changes.

Answer 11

o Adiabatic → no heat exchange across boundaries of a system o Isobaric → constant pressure, but boundaries of the system can change (volume changes)

Question 12

STABLE VS. METASTABLE EQUILIBRIUM

Answer 12

• Stable equilibrium - System is at its lowest possible energy level. • Metastable equilibrium - System satisfies above two criteria but is not at lowest possible energy.

Question 13

Define enthalphy and entropy.

Answer 13

Enthalpy is the measure of total heat present in the thermodynamic system where the pressure is constant. It is represented as. Δ H = Δ E + P Δ V. where E is the internal energy, P is the pressure and E is the energy. Entropy is the measure of disorder in a thermodynamic system.

Question 14

Define Gibbs Free energy.

Answer 14

Gibbs free energy, also known as the Gibbs function, Gibbs energy, or free enthalpy, is a quantity that is used to measure the maximum amount of work done in a thermodynamic system when the temperature and pressure are kept constant.

Question 15

What do you mean by Fugacity?

Answer 15

• The partial pressure a real gas would have if it were ideal. • Fugacity is applied to reactions among real gases.

Question 16

Enumerate examples of iron type meteorite.

Answer 16

Troilite, hexahedrite, octahedrite, and ataxite.

Question 17

Define what is Van ‘t Hoff equation and explain where it can be used.

Answer 17

The Van ‘t Hoff equation has been widely utilized to explore the changes in state functions in a thermodynamic system. The Van ‘t Hoff plot, which is derived from this equation, is especially effective in estimating the change in enthalpy and entropy of a chemical reaction.

Question 18

What do you mean by the term “Loss of Ignition”?

Answer 18

Loss of Ignition is the weight loss that occurs when the powdered sample is heated to 700-800 deg Celcius, at which point all the remaining volatiles are released. The lower the value the more fresh the samples.

Question 19

Define what is meant by Diadochy.

Answer 19

The ability of different elements to occupy the same lattice position in a particular crystal. Ex. Forsterite and Fayalite

Question 20

Enumerate the common minerals that a meteorite has.

Answer 20

Kamacite, taenite, pyroxene, olivine, and plagioclase

Question 21

Describe a principal quantum number.

Answer 21

The greater this number, the farther away from the nucleus the electrons will reside, have higher energy, and less stability.

Question 22

Explain the Goldschmidth’s Rule for Ionic Substitution.

Answer 22

1. The ions of one element can extensively replace those of another in ionic crystals if their radii differ by less than approximately 15%. 2. Ions whose charges differ by one unit substitute readily for one another provided electrical neutrality of the crystal is maintained. If the charges differ by more than one unit, substitution is generally slight. 3. When two different ions can occupy a particular position in a crystal lattice, the ion with the higher ionic potential forms a stronger bond with the anions surrounding the site.

Question 23

Based from your previous answer, kindly explain how Ringwood has modified the Goldschmidth’s Rule for Ionic Substitution.

Answer 23

Substitutions may be limited, even when the size and charge criteria are satisfied, when the competing ions have different electronegativities and form bonds of different ionic character. This rule was proposed in 1955 to explain discrepancies with respect to the first three Goldschmidt rules. For example, Na+ and Cu+ have the same radius and charge, but do not substitute for one another.

Question 24

Explain how incompatible and compatible trace elements differ from each other and site examples for each.

Answer 24

Incompatible elements: Elements that are too large and/or too highly charged to fit easily into common rock-forming minerals that crystallize from melts. These elements become concentrated in melts. Compatible elements: Elements that fit easily into rock-forming minerals, and may in fact be preferred, e.g., Cr, V, Ni, Co, Ti, etc. (“Under incompatible elements Large-ion lithophile elements (LIL’s): Incompatible owing to large size, e.g., Rb+, Cs+, Sr2+, Ba2+, (K+).
High-field strength elements (HFSE’s): Incompatible owing to high charge, e.g., Zr4+, Hf 4+, Ta4+, Nb5+, Th4+, U4+, Mo6+, W6+, etc.”)

Question 25

Explain how camouflage substitution (a type of trace-element substitution) works.

Answer 25

• Occurs when the minor element has the same charge and similar ionic radius as the major element (same ionic potential; no preference. • Zr4+ (0.80 Å); Hf4+ (0.79 Å) • Hf usually does not form its own mineral; it is camouflaged in zircon (ZrSiO4)

Question 26

Explain how capture substitution (a type of trace-element substitution) works.

Answer 26

• Occurs when a minor element enters a crystal preferentially to the major element because it has a higher ionic potential than the major element. • For example, K-feldspar captures Ba2+ (1.44 Å; Z/r = 1.39) or Sr2+ (1.21 Å; Z/r = 1.65) in place of K+ (1.46 Å, Z/r = 0.68). • Requires coupled substitution to balance charge: K+ + Si4+ « Sr2+ (Ba2+) + Al3+

Question 27

Explain how admission substitution (a type of trace-element substitution) works.

Answer 27

• Involves entry of a foreign ion with an ionic potential less than that of the major ion. • Example Rb+ (1.57 Å; Z/r = 0.637) for K+ (1.46 Å, Z/r = 0.68) in K-feldspar. • The major ion is preferred.

Question 28

What do you mean by distribution (partition) coefficient and how does it affect the type of substitution in trace elements?

Answer 28

Partition coefficients relate the amount of a trace element that enters a growing crystal to the amount of that element in the coexisting fluid. These coefficients are constants and are characteristic of each mineral species.

Question 29

Differentiate exothermic and endothermic reactions in terms of heat flow.

Answer 29

An exothermic process releases heat, causing the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings.

Question 30

If there is 0.6 g of Pb present in 277 g of solution, what is the Pb concentration in parts per thousand?

Answer 30

(0.6gPb/277gsolution) × 1000 = 2.17 ppth

Question 31

This is where two phases could never coexist.

Answer 31

Peritectic

Question 32

The geochemical signature of mantle derive magma

Answer 32

Cr#

Question 33

This element indicates pyroxene fractionation as it is concentrated in pyroxenes;

Answer 33

Sc - Scandium

Question 34

This elements is commonly incompatible and strongly partitioned into garnet and amphibole

Answer 34

Y - Yttrium

Question 35

What is the test similar to the Becke Line Test but used in mineragraphy?

Answer 35

Kalb Light Line

Question 36

He regarded living organisms as “most powerful geological force”. According to him, Earth’s crust originated from the
biosphere.

Answer 36

Vladimir Ivanovich Vernadsky

Question 37

What is the Hubble’s constant?

Answer 37

15 km/s/10^6 light years

Question 38

As temperature reach _________ : ________ occurs which is the formation of stars.

Answer 38

20x10^6K : Hydrogen Fusion

Question 39

How old is the sun?

Answer 39

Sun : middle age (4.5x10 9 years old) ‐ has enough H to last 10x10 9 years

Question 40

Differentiate invariant, univariant, and divariant in the sense of Gibbs Phase Rule.

Answer 40

Invariant - This imply that the phase equilibrium assemblage completely constrains the state of the system to a particular P and T. Univariant - Indicate the state of the system is only constrained in one direction which is along the phase boundary. Divariant - Showing that the pressure and temperature can vary independently

Question 41

What do you mean by “batch melting”.

Answer 41

A closed system process where all melt remains in contact and equilibrium with the residue.

Question 42

Define fractional crystallization.

Answer 42

An open system process in which each increment of solid is immediately removed from the system as it forms. Ex: Bowen’s Reaction Series

Question 43

Define Tholeiites.

Answer 43

They are lower pressure and larger percent of partial melting; Occur in convergent and divergent plate margin, oceanic and continental intraplate; Almost all the basalt found on the moon is in this type.

Question 44

Basaltic melts can be created through

Answer 44

Decompression melting (in divergent and intraplate) and fluid fluxing (in subduction)

Question 45

Enumerate examples of Light Rare earth elements (LREE).

Answer 45

Sc, La, Ce, Pr, Nd, Pm, Sm, Eu

Question 46

Enumerate examples of Heavy rare earth elements (HREE).

Answer 46

Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu

Question 47

What is a Harker Diagram?

Answer 47

Bivariate diagrams showing the relative content relationship of oxide compounds as the magma evolves

Question 48

Provide the measurement of electrode separation for short and long normal log.

Answer 48

Short normal log (16 inches), Long normal log (64 inches)

Question 49

What are the evidences that the Universe is expanding?

Answer 49

a) Red Shift ‐ moving away; Doppler Effect; increase in wavelength • Blue Shift ‐ moving towards b) Cosmic Microwave Radiation (Background Radiation) : remnant of the beginning of universe.

Question 50

Enumerate the heirarchy of heavenly bodies.

Answer 50

1. Atoms H and He 2. Molecules 3. Dust particles 4. Meteoroids 5. Asteroids 6. Comets 7. Satellites 8. Planets 9. Stars 10. Galaxies 11. Clusters of Galaxie

Question 51

Enumerate the 4 Galilean satellites of Jupiter.

Answer 51

• Io is the most volcanically active in the solar system. The surface is yellow to red due to the sulfur from volcanic eruptions. • Europa is covered by frozen ocean. Crisscross on the surface are ice dikes, which formed when fractures and meteorite impacts are filled with water. Smallest Galilean satellite. • Ganymede’s dark color is water ice mixed with impurities. It is the biggest Galilean satellite. • Callisto is the outermost of the Galilean satellites. It is heavily cratered icy crust. Valhalla and Asgard are its two prominent craters.

Question 52

Explain how Atomic absorption spectroscopy (AAS) works.

Answer 52

Atomic absorption spectrometry (AAS) detects elements in either liquid or solid samples through the application of characteristic wavelengths of electromagnetic radiation from a light source. This is the geochemical technique used for biological or trace element analyses, quantitative analysis for metals and concentration of analytes.

Question 53

Will the universe expand forever?

Answer 53

‐ can’t be concluded since scientists don’t know the definite amount of matter. Therefore we can say that the universe has “Finite Size”. ‐ if we know the total amount of matter, its enough to conclude that if there are enough mass to say if it can contract again.

Question 54

Explain how Inductively coupled plasma mass spectrometry (ICP-MS) can be used in the study of geochemistry.

Answer 54

Inductively coupled plasma mass spectrometry (ICP-MS) represents a major geochemical tool for both elemental and isotope ratio analysis . It allows analyses of elements at concentrations as low as 1 part per trillion (ppt) or even lower depending on instrument and application. It is used for isotope analysis, forensic studies and toxicology.

Question 55

Explain the mechanism of a black body in the galaxy.

Answer 55

A black body is an idealized object that absorbs all electromagnetic radiation it comes in contact with. It then emits thermal radiation in a continuous spectrum according to its temperature. Stars behave approximately like blackbodies, and this concept explains why there are different colors of stars.

Question 56

How does the triple-alpha process occur?

Answer 56

In the triple-alpha process, stars fuse together three alpha particles, creating a new particle with six protons and six neutrons. This is the universe’s most common form of carbon.

Question 57

What happened during T-Tauri Stage?

Answer 57

• T‐Tauri Stage – Superluminous phase of the sun caused by the expulsion of about 25% of the mass in the form of solar wind. During this stage, the volatile gases are removed from the rotating disc. Planetesimals that are greater than 10 meters will be the ones left.

Question 58

What is Titus-Bode Law? Enumerate the radius of the 10 planetary bodies from this specific law.

Answer 58

• Titus‐Bode Law predicts the distances of the planets from the Sun in terms of astronomical unit (AU). It is derived by using the numbers 0, 3, 6, 12, to each number, and divide the result by 10. The final results are the Titus‐Bode numbers (0.4, 0.7, 1.0, 1.6, 2.8…)