General Chem HW 1. You have a chemical sealed in a glass container filled with a
ID: 933847 • Letter: G
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General Chem HW
1. You have a chemical sealed in a glass container filled with air. The glass container has a mass of 200.0 grams and the chemical has a mass of500 grams. The total mass of the setup is 700 grams. The chemical is ignited by means of a magnifying glass focusing sunlight onto the reactant. After the chemical has completely burned, what is the total mass of the setup?
_______ grams
2. Dalton assumed that all atoms of the same element were identical in all their properties. Explain why this assumption is not valid.
3. Each of the following statements is true, but Dalton might have had trouble explaining some of them with his atomic theory. Give explanations for the following statements.
(a) The space-filling models for ethyl alcohol and dimethyl ether are shown below.
These two compounds have the same composition by mass (52% carbon, 13% hydrogen, and 35% oxygen), yet the two have different melting points, boiling points, and solubilities in water.
(b) Burning wood leaves an ash that is only a small fraction of the mass of the original wood.
(c) Atoms can be broken down into smaller particles.
(d) One sample of lithium hydride is 87.4% lithium by mass, while another sample of lithium hydride is 74.9% lithium by mass. However, the two samples have the same properties.
General Chem HW 1. You have a chemical sealed in a glass container filled with air. The glass container has a mass of 200.0 grams and the chemical has a mass of500 grams. The total mass of the setup is 700 grams. The chemical is ignited by means of a magnifying glass focusing sunlight onto the reactant. After the chemical has completely burned, what is the total mass of the setup? _______ grams 2. Dalton assumed that all atoms of the same element were identical in all their properties. Explain why this assumption is not valid. 3. Each of the following statements is true, but Dalton might have had trouble explaining some of them with his atomic theory. Give explanations for the following statements. (a) The space-filling models for ethyl alcohol and dimethyl ether are shown below. These two compounds have the same composition by mass (52% carbon, 13% hydrogen, and 35% oxygen), yet the two have different melting points, boiling points, and solubilities in water. (b) Burning wood leaves an ash that is only a small fraction of the mass of the original wood. (c) Atoms can be broken down into smaller particles. (d) One sample of lithium hydride is 87.4% lithium by mass, while another sample of lithium hydride is 74.9% lithium by mass. However, the two samples have the same properties.Explanation / Answer
1. If it is sealed, then nothing came out, nothing got in, and the law of conservation of mass applies. Mass thus remained the same at 600 g.
2. an atom which is an isotope has a different number of neutrons then the average atom of that element. now, understanding that the masses we have for atoms are averages, that means that each one has a different value. that means that by default they are not all the same.
3.One word: Isotopes. Three words: Isotopes of hydrogen.
Longer: "Lithium hydride" means "LiH". If the hydrogen contains one proton and no neutrons, its mass is ~1 and the "lithium hydride is 87.4% lithium by mass". If the hydrogen is really "heavy hydrogen" (deuterium, symbol D, mass ~2), then the "lithium hydride" is actually "lithium deuteride", 74.9% lithium by mass.
Isotopes hadn't been discovered when Dalton worked out his theory, which is why he would've been stumped
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