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:
a. fluorine
Explanation:
Fluorine is the element of group 17 and period 2. The electronic configuration of the element is 
.
Stable oxidation state = -1 of fluorine as it gains one electron to gain noble gas configuration.
With alkali metals, which have oxidation state of +1 form ionic compound of the form, MX where X is F.
Among the halogens, fluorine forms the most stable halide because of the comparable size of the hydrogen and fluorine. Thus, it is the weakest acid when compared with other hydrogen halides.
Fluorine is the most reactive in the halogen series and thus, combines with most of the elements.
Fluorine forms inter-halogen compounds of form XA only. Example - ClF.
Hence, option a is correct.
Answer:
d
Explanation:
from you know the atomic number it should be easy to find
The answer is <span>ionic aluminum fluoride (</span>AlF3). Note that boiling points of pure solvents are raised in the presence of solutes. The type of solute also affects the boiling point elevation of the solution. Ionic substances tend to raise it more than covalent ones, so sucrose is out of the picture. Next, consider the number of ions the ionic substance produces. The more ions, the greater the BPE. AlF3 dissociates into 4 ions.
0.326 moles of gas
Explanation:
Knowing the volume of a gas at standard temperature and pressure (STP) we may calculate the number of moles of the gas using the following formula:
number of moles = volume / 22.4 (L /mole)
number of moles of gas = 7.3 (L) / 22.4 (L /mole)
number of moles of gas = 0.326 moles
Learn more about:
molar volume
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