Complete Question:
To aid in the prevention of tooth decay, it is recommended that drinking water contain 0.800 ppm fluoride. How many grams of F− must be added to a cylindrical water reservoir having a diameter of 2.02 × 102 m and a depth of 87.32 m?
Answer:
2.23x10⁶ g
Explanation:
The concentration of the fluoride (F⁻) must be 0.800 ppm, which is 0.800 parts per million, so the water must have 0.800 g of F⁻/ 1000000 g of the solution. The density of the water at room temperature is 997 kg/m³ = 997x10³ g/m³. So, the concentration of the fluoride will be:
0.800 g of F⁻/ 1000000 g of the solution * 997x10³ g/m³
0.7976 g/m³
The volume of the reservoir is the volume of the cylinder: area of the base * depth. The base is a circumference, which has an area:
A = πR², where R is the radius = 1.01x10² m (half of the diameter)
A = π*(1.01x10²)²
A = 32047 m²
The volume is then:
V = 32047 * 87.32
V = 2.7983x10⁶ m³
The mass of the F⁻ is the concentration multiplied by the volume:
m = 0.7976 * 2.7983x10⁶
m = 2.23x10⁶ g
Answer:
Oxygen is in excess.
Explanation:
The coefficients of the balanced equation create a mole ratio that shows the ratio of how many reactants are used up and products are created.
The mole ratio of Mg to O2 in this equation is 2:1, which means that for every two moles of Mg used, there will be 1 mole of O2 used.
If we have 3.00 moles of Mg, we will only need 1.5 moles of oxygen to completely burn the Mg. Therefore, when all 3.00 moles of Mg are used, there will still be some of the 2.20 moles of oxygen remaining.
<span>The generalized reaction for chemical decomposition is: AB → A + B
NaOH is sodium hydroxide. When sodium and water is combined it makes sodium hydroxide and hydrogen
When sodium hydroxide decomposes under thermal decomposition, it breaks down into sodium oxide and water.
Thus, </span><span>C) 2NaOH Na2O + H2O</span>
According to table N, the isotopes uranium-238 and uranium-235 have different half lives.
<h3>What are radioactive nuclides?</h3>
Radioactive nuclides are those nuclides that are able to undergo radioactive decay. They have specific modes of decay that is peculiar to each isotope.
Hence, according to table N, the isotopes uranium-238 and uranium-235 have different half lives.
Learn more about uranium-238:brainly.com/question/9099776
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