Answer:
21.5 g.
Explanation:
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In this case, since the reaction between the given compounds is:

We can see that according to the law of conservation of mass, which states that matter is neither created nor destroyed during a chemical reaction, the total mass of products equals the total mass of reactants based on the stoichiometric proportions; in such a way, we first need to compute the reacted moles of Li3P as shown below:

Now, the moles of Li3P consumed by 15 g of Al2O3:

Thus, we infer that just 0.29 moles of 0.73 react to form products; which means that the mass of formed products is:

Therefore, the total mass of products is:

Which is not the same to the reactants (53 g) because there is an excess of Li₃P.
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Answer: Heterogenous mixtures are the ones in which we can see the different components clearly. Air is considered to be homogenous, because we don't see the different noble gases' particles floating around. Salt water is also homogenous, because salt dissolves almost completely into water, becoming hard to see without the proper equipment salt particles in it. Steel is also homogenous, since the metals that compose it are mixed during the heating. The only heterogenous would be soil, because we can see different particles in it, with different sizes, shapes, colors, etc without having to use special equipment.
53.6 hectometers is not equal to 0.536 kilometer
I believe the major periodic trends include; electronegativity, ionization energy, electron affinity, atomic radius, melting point, and the metallic character. Periodic trends, arising from the arrangement of the periodic table, provide chemists with an invaluable tool to quickly predict an element's property.