A 250 gram sample of water at the boiling point had 45.0 kj of heat added. how many grams of water were vaporized? heat of vapor
1 answer:
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The question is incomplete, here is the complete question:
Aqueous sulfuric acid reacts with solid sodium hydroxide to produce aqueous sodium sulfate and liquid water. If 12.5 g of water is produced from the reaction of 72.6 g of sulfuric acid and 77.0 g of sodium hydroxide, calculate the percent yield of water. Be sure your answer has the correct number of significant digits in it.
<u>Answer:</u> The percent yield of water in the reaction is 46.85 %.
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
.....(1)
- <u>For NaOH:</u>
Given mass of NaOH = 77.0 g
Molar mass of NaOH = 40 g/mol
Putting values in equation 1, we get:
- <u>For sulfuric acid:</u>
Given mass of sulfuric acid = 72.6 g
Molar mass of sulfuric acid = 98 g/mol
Putting values in equation 1, we get:
The chemical equation for the reaction of NaOH and sulfuric acid follows:
By Stoichiometry of the reaction:
1 mole of sulfuric acid reacts with 2 moles of NaOH
So, 0.741 moles of sulfuric acid will react with = of NaOH
As, given amount of NaOH is more than the required amount. So, it is considered as an excess reagent.
Thus, sulfuric acid is considered as a limiting reagent because it limits the formation of product.
By Stoichiometry of the reaction:
1 mole of sulfuric acid produces 2 moles of water
So, 0.741 moles of sulfuric acid will produce = of water
Now, calculating the mass of water from equation 1, we get:
Molar mass of water = 18 g/mol
Moles of water = 1.482 moles
Putting values in equation 1, we get:
To calculate the percentage yield of water, we use the equation:
Experimental yield of water = 12.5 g
Theoretical yield of water = 26.68 g
Putting values in above equation, we get:
Hence, the percent yield of water in the reaction is 46.85 %.
The rate at which radioactive substances disintegrate is a constant for a
given radioactive material.
- <u>The fossil is 710 million years old</u>.
Reasons:
The half-life of a radioactive material is the time it takes half of the nucleus
of a radioactive material to disintegrate into other forms of materials
through the given off of energy and particles.
The half life of Uranium 235 = 710 million years
The product of the decay of Uranium 235 = Lead 207
The mass of Uranium 235 in the fossil = 4 micrograms
The mass of Lead 207 in the sample = 4 micrograms
Therefore, the mass of Lead 207 in the fossil is equal to the mass of
Uranium 235, therefore, a minimum of half of the Uranium 235 has
decomposed, which gives;
The time of decomposition of the Uranium 235 = 1 Half life = 710 million years
The age of the fossil = The time in which the Uranium has been
decomposing = The time of decomposition = 1 half life of Uranium 235 = 710
million years
- <u>The age of the fossil = 710 million years</u>
Using the formula for half-life, we get;
The fossil contains initially only Uranium 235 with a minimum mass of 4 mg
+ 4 mg = 8 mg, which gives;
N₀ = 8 mg
N(t) = The current mass of Uranium 235 = 4 mg
= 710 million years
Therefore;
t = 710
- <u>The age of the fossil, </u><u><em>t</em></u><u> = 710 million years</u>
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Answer:
Dipole-dipole attractions
Explanation:
The Cl atom is more electronegative than H, so it attracts the electrons in the H-Cl bond more to itself.
The Cl end of the molecule becomes partially negative (δ-), and the H end becomes more positive (δ+). This separation of charge is called an electric dipole,
When two HCl molecules are near each other, they arrange themselves so that the negative and positive ends of the dipoles line up and attract the two molecules together.
