Answer:
Regional metamorphic rocks form from other rocks (protoliths) by changes in mineralogy and texture in response to changing physical conditions (temperature, lithostatic pressure, and, in most cases, shear stress). Regional metamorphism occurs over broad areas in the lithosphere, possibly influenced by the heat supply. Regional metamorphic rock results from regional metamorphism and usually develops a flaky texture. These changes are essentially solid-state reactions, but very often a fluid phase is present, either participating in the reaction or as a reaction medium. Many regional metamorphic rocks have a chemical composition that is very similar to that of their sedimentary or igneous precursors, with the exception of removal or addition of volatiles (mainly H2O and CO2). This type of behavior is termed isochemical metamorphism. Metamorphism may also take place as a result of a change in chemical environment; this may occur by transport of elements between chemically contrasting rock types (e.g., formation of calc-silicate minerals at a quartzite–marble contact) or by circulation of fluids that dissolve some substances and precipitate others. This process of significant chemical change during metamorphism is known as allo-chemical metamorphism or metasomatism, and rocks formed in this manner are metasomatic rocks. Metasomatism is, however, mostly of local significance, and the total volume of metasomatic rocks in regional metamorphic terranes is rather minor. The distinction between metasomatism and is chemical metamorphism is also a matter of scale. On the scale of individual grains, mass transport takes place during all phase transformations; on the scale of a thin section, it is probably the rule for regional metamorphism; on the scale of a hand (sized) specimen, it can be observed frequently; and on a larger scale, it is the exception.
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Answer:
Empirical formula: BH3
Molecular Formula: B2H6
Explanation:
To solve the exercise, we need to know how many boron atoms and how many hydrogen atoms the compound has. We know that of the total weight of the compound, 78.14% correspond to boron and 21.86% to hydrogen. As the weight of the compound is between 27 g and 28 g, using the above percentages we can solve that the compound has between 21.1 g and 21.8 g of boron, and between 5.9 g and 6.1 g of hydrogen:
100% _____ 27 g
78.14% _____ x = 78.14% * 27g / 100% = 21.1 g boron
100% ______27 g
21.86% ______ x = 21.86% * 27g / 100% = 5.9 g hydrogen
100% _____ 28 g
78.14% _____ x = 78.14% * 28g / 100% = 21.8 g boron
100% _____ 28g
21.86% _____ x = 21.86% * 28g / 100% = 6.1 g hydrogen
So, if the atomic weight of boron is 10.8 g, there must be two boron atoms in the compound that sum 21.6 g. The weight of hydrogen is 1 g, so the compound must have six hydrogen atoms.
The molecular formula represents the real amount of atoms that form a compound. Therefore, the molecular formula of the compound is B2H6.
The empirical formula is the minimum expression that represents the proportion of atoms in a compound. For example, ethane has 2 carbon atoms and 6 hydrogen atoms, so its molecular formula is C2H6, however, its empirical formula is CH3. Therefore, the empirical formula of the boron compound is BH3.
Answer:
Solve the following problems (assuming constant temperature). Assume all numbers are 3 sig figs. 1. A sample of oxygen gas occupies a volume of 250 mL at 740 torr pressure. ... the gas exert if the volume was decreased to 2.00 liters? ... A 175 mL sample of neon had its pressure changed from 75.0 kPa to 150 kPa.
Explanation:
The partial atmospheric pressure (atm) of hydrogen in the mixture is 0.59 atm.
<h3>How do we calculate the partial pressure of gas?</h3>
Partial pressure of particular gas will be calculated as:
p = nP, where
- P = total pressure = 748 mmHg
- n is the mole fraction which can be calculated as:
- n = moles of gas / total moles of gas
Moles will be calculated as:
- n = W/M, where
- W = given mass
- M = molar mass
Moles of Hydrogen gas = 2.02g / 2.014g/mol = 1 mole
Moles of Chlorine gas = 35.90g / 70.9g/mol = 0.5 mole
Mole fraction of hydrogen = 1 / (1+0.5) = 0.6
Partial pressure of hydrogen = (0.6)(748) = 448.8 mmHg = 0.59 atm
Hence, required partial atmospheric pressure of hydrogen is 0.59 atm.
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The number of molecules decrease
