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Law of Definite Proportions

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1. Calculate and record the following for the experiment performed with 20g KClO3:

(a) mass of the crucible with manganese(IV) dioxide (in grams): 53.300g
(b) mass of the crucible after potassium chlorate has been added (in grams): 73.300g
(c) mass of the crucible after heating (in grams): 21.00 degrees C
(d) mass of potassium chloride (in grams): 8.64
(e) mass of oxygen in sample of potassium chlorate (in grams): 65.367g
(f) mass percent of oxygen in potassium chlorate:

2. Calculate a theoretical mass percent of oxygen in KClO3 according to:

theoretical mass percent of oxygen = (mass of 3 oxygen atoms) / (mass of KClO3)

3. Calculate the percent error in the experiment using the experimental and theoretical values of the mass percent of oxygen. The percent error is defined as:

|(experimental value) - (theoretical value)| / theoretical value * 100%

4. How well does your experimental result match the theoretical value? What sources of error may explain the discrepancy?

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https://brainmass.com/chemistry/law-of-definite-proportions/law-of-definite-proportions-43973

Solution Preview

1. Calculate and record the following for the experiment performed with 20g KClO3:

(a) mass of the crucible with manganese(IV) dioxide (in grams): 53.300g

(b) mass of the crucible after potassium chlorate has been added (in grams): 73.300g

(c) mass of the crucible after heating (in grams):
If the mass of potassium chloride is 8.64 g and the mass of crucible is 53.500 g, then, the mass of crucible after heating (that's including potassium chloride) should be 62.14 g (from adding 8.64 g and 53.500 g)

(d) mass of potassium chloride (in grams): 8.64

(e) mass of oxygen ...

Solution Summary

This solution deals with calculating results for an experiment that involves 20 grams of KClO3. This solution also answers why discrepancies might exist in the calculations.

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Chemistry Multiple Choice Quiz with Answer Grid

I am preparing for my chemistry exam and would appreciate a multiple choise quiz on the last chapter (i.e., ideal gas law, superconductivity, extensive properties, critical pressure, aerobic, etc.). Can you provide me with such a quiz with the answers provided. Thanks.

Chemistry Quiz 2: Multiple Choice Questions

1) Elements cannot be decomposed by chemical means, but can be decomposed by physical means.
(a) True
(b) False

2) According to the Bronsted-Lowry model, bases are proton acceptors.
(a) True
(b) False

3) Pick the correct statement:
(a) Le Chatelier's principle deals with equilibrium.
(b) Le Chatelier's principle deals with an ideal gas.
(c) Le Chatelier's principle deals with dispersion forces.

4) An ideal gas needs to follow which laws perfectly?
(a) John Dalton's law, Faraday's law
(b) Charles's law, Boyle's law, Avogadro's law
(c) Raoult's law, Charles's law
(d) Boyle's law, Gay-Lussac's law

5) Superconductivity means very low electrical resistance.
(a) True
(b) False

6) The ideal gas law can be written as ...
(a) P 1V1/T1 = P2V2/T2
(b) PV = nRT

7) Partial pressure is the pressure of one gas in a mixture of gases.
(a) True
(b) False

8) When a gas flows through a small hole of its container, this is called ...
(a) diffusion
(b) effusion
(c) osmosis

9) One atmosphere is around 101 kPa.
(a) True
(b) False

10) Pick the right statement:
(a) An extensive property depends on how much matter is present.
(b) An intensive property depends on how much matter is present.

11) Is this correct?
Hund's rule discusses the partial pressures of a gas.
(a) True
(b) False

12) The law of constant composition is also called the law of multiple proportions.
(a) True
(b) False

13) Pick the wrong statement:
(a) London dispersion forces are intermolecular forces.
(b) London dispersion forces are intramolecular forces.

14) Molar heat capacity is the heat required to raise the temperature of a mole of a substance by 10 K.
(a) True
(b) False

15) Are the regions for all orbitals with the same principal quantum number called shells?
(a) yes
(b) no

16) pH is a measure of acidity (pH is the measure of the concentration of H+ ions).
(a) True
(b) False

17) Aerobic processes need ...
(a) hydrogen
(b) oxygen
(c) helium

18) Dispersion forces are repulsive forces in an ideal gas.
(a) correct
(b) incorrect

19) Are photons very heavy?
(a) Yes
(b) No

20) At critical pressure ...
(a) an ideal gas becomes a solid
(b) a liquid becomes a solid
(c) a gas becomes a liquid

Thank you very much!

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