Quan used a beaker to prepare a solution consisting of 4 g of a reddish powder and 35 g of alcohol. As soon as the substances mi
xed together, he covered the beaker tightly so that no gas could escape. After the powder dissolved, he noticed a black solid fell to the bottom of the test tube. As part of his observation, he weighed the solution with the black solid. What did he find?
<em>That the total mass of the final solution with the black solid, inside the covered beaker, was equal to 39 g.</em>
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Explanation:
The formation of a <em>black solid</em> that <em>fell to the bottom</em> of the test tube is the indication of a chemical reaction: the <em>4 g of reddish powder</em> and the <em>35 g of alcohol</em> reacted with each other and formed new substances.
The chemical reactions obey the law of conservation of mass: the mass of the reactants is equal to the mass of the products.
Since the beaker was tightly covered, none of the substances escaped, and all the products are present inside the beaker along with the reactants that were left over, in case some of them did not react to completion.
Therefore, the mass of the content of the beaker, after reaction, must be equal to the mass of the initial substances: 4 g + 35 g = 39g.
Atomic radius decreases across a period because valence electrons are being added to the same energy level at the same time the nucleus is increasing in protons. The increase in nuclear charge attracts the electrons more strongly, pulling them closer to the nucleus.
Simply because we see Claudia used a shortcut. Tom uses more physical force than Claudia, since Claudia only had to push the boxes into there required shelves.
