Laws of Chemical Combination: 30 flashcards
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1. State the Law of Conservation of Mass.
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Mass is neither created nor destroyed in a chemical reaction; total mass of reactants equals total mass of products in a closed system.
2. Who proposed the Law of Conservation of Mass?
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Antoine Lavoisier (1789).
3. State the Law of Definite Proportions.
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A given compound always contains the same elements in the same proportion by mass, regardless of source or method of preparation.
4. Who proposed the Law of Definite Proportions?
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Joseph Proust (1799).
5. State the Law of Multiple Proportions.
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If two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers.
6. Who proposed the Law of Multiple Proportions?
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John Dalton (1803).
7. State Gay-Lussac's Law of Gaseous Volumes.
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Gases combine or are produced in a simple ratio by volume at the same temperature and pressure.
8. Who proposed Gay-Lussac's Law of Gaseous Volumes?
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Joseph Louis Gay-Lussac (1808).
9. State Avogadro's Law.
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Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules.
10. Who proposed Avogadro's Law?
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Amedeo Avogadro (1811).
11. What is the mass ratio of H to O in water ($H_2O$)?
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$1:8$ (hydrogen : oxygen by mass).
12. How do CO and $CO_2$ illustrate the Law of Multiple Proportions?
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For a fixed mass of carbon (12 g), oxygen masses are 16 g in CO and 32 g in $CO_2$, giving a ratio of $1:2$.
13. Which law explains why 1 mole of any gas occupies 22.4 L at STP?
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Avogadro's Law.
14. What is the mass ratio of C to O in $CO_2$?
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$12:32 = 3:8$.
15. What is the mass ratio of C to O in CO?
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$12:16 = 3:4$.
16. What is Avogadro's number?
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$6.022 \times 10^{23}$ molecules per mole.
17. What is the molar volume of any ideal gas at STP?
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$22.4\,\text{L}$.
18. Which law is used to balance chemical equations?
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Law of Conservation of Mass.
19. Which law helps calculate percentage composition of a compound?
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Law of Definite Proportions.
20. Which law is used to determine molecular formulas from empirical formulas?
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Law of Multiple Proportions.
21. Does the Law of Conservation of Mass hold in nuclear reactions?
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No; in nuclear reactions mass is converted to energy via $E = mc^2$.
22. Does Gay-Lussac's Law apply to solids and liquids?
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No; it applies only to gases.
23. Does Avogadro's Law apply at different temperatures and pressures?
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No; it applies only at identical temperature and pressure.
24. What is the key difference between Definite and Multiple Proportions?
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Definite Proportions deals with one compound; Multiple Proportions deals with two or more compounds of the same elements.
25. Which law is illustrated by $2$ volumes $H_2$ + $1$ volume $O_2$ $\rightarrow$ $2$ volumes $H_2O$ vapour?
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Gay-Lussac's Law of Gaseous Volumes.
26. Give an example of oxides of nitrogen illustrating the Law of Multiple Proportions.
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$N_2O$, $NO$, $NO_2$, $N_2O_5$ — for fixed nitrogen mass, oxygen masses are in simple whole-number ratios.
27. What is the ratio of oxygen masses in $N_2O$ and NO for fixed nitrogen mass?
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$1:2$.
28. What is the experimental basis of Dalton's Atomic Theory?
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The Laws of Chemical Combination.
29. In $10.0\,\text{g}$ $CaCO_3$ decomposition, $5.6\,\text{g}$ CaO and $4.4\,\text{g}$ $CO_2$ form. Which law is illustrated?
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Law of Conservation of Mass ($5.6 + 4.4 = 10.0\,\text{g}$).
30. Which law connects volumes to moles for gases?
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Avogadro's Law (with Gay-Lussac's Law).
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