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From thermogravimetric analysis of a 0.7g desiccated sample you find that 5.2% of mass is lost before 150C. You also find that 26.5% of the mass is lost between 150 and 500C. Finally, 23.4% of the mass is lost near 840C. By other means, you know this soil is devoid of Si but high in Ca and Fe. What are the likely phases present? Be as specific as you can. For example, metal oxide is bad. Giving the exact stoichiometry for the most likely metal oxide is good.

User Hko
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2 Answers

5 votes

Answer:

The first 5.2% loss of mass (0.036 g) will be organic matter below 150 C.

Mass of organic matter that is below 150°C = 0.052 ×0.7 = 0.036 g

Mass of minerals that is below 500°C = 26.5% of 0.7g which is,

= 0.265 × 0.7

Mass of minerals that is below 500°C = 0.186 g

Mass of calcium below 840°C = 23.5% of 0.7 which is

= 0.235 × 0.7

Mass of calcium below 840°C = 0.165 g

NB - The melting point of calcium is 840°C

The mass of Iron = 0.7 - (0.036 + 0.186 + 0.165)

Mass of Iron oxide = 0.313g

Step-by-step explanation:

Thermogravimetric analysis is a method of thermal analysis that encompasses all processes by which the mass of a sample is measured overtime as the temperature changes. The technique in involves the monitoring of the mass of a sample against time or temperature, and this is performed with a ThermoGravimetric Analyser (TGA) or thermobalance. Weight loss information is useful in the characterization of materials, with examples such as polymers, soils, or adhesives, and in problem solving.

The changes in the mass can be as a result of a variety processes which include decomposition, degradation, sublimation, vaporization, adsorption, desorption, oxidation, and reduction.

A Thermogravimetric analysis is performed by steadily raising the temperature of a sample in a furnace as its weight is measured on an analytical balance that remains outside of the furnace. In thermogravimetric analysis , mass loss is observed if a thermal event involves loss of a volatile component.

From the information given above,

The soil consists of water, organic matter, minerals, and air. These are basically what the soil comprises of.

The sample for Thermogravimetric Analysis was taken in 0.7 g.

The first 5.2% loss of mass will be organic matter below 150 C.

the next 26.5% loss of mass will be minerals below 500 C

The next 23.5% loss of mass will be calcium at 840 C (Calcium metling point is 840C)

the remaining will be Iron oxide which comes to 0.37 g.

User Shijin
by
4.9k points
4 votes

Answer:

Check below for answers and explanations

Step-by-step explanation:

The components of the soil are organic matter, minerals, calcium and iron.

Let us find the masses of the individual components

Mass of the dessicated sample, M = 0.7 g

For the 5.2% loss in mass:

Mass of organic matter below 150°C = 5.2% of 0.7g

Mass of organic matter below 150°C = 0.052*0.7 = 0.0364 g

Mass of minerals below 500°C = 26.5% of 0.7g

Mass of minerals below 500°C = 0.265 * 0.7

Mass of minerals below 500°C = 0.1855 g

Mass of calcium below 840°C = 23.5% of 0.7

Mass of calcium below 840°C = 0.235 * 0.7

Mass of calcium below 840°C = 0.1645 g

Note: The melting point of calcium is 840°C

The mass of Iron = 0.7 - (0.0364 + 0.1855 + 0.1645)

Mass of iron = 0.3136 g

User Andy Britcliffe
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5.1k points