Explanation:
The chemical formula magnesium sulfide written as MgS and NOT 
because charge on magnesium ion is +2 and charge on sulfide ion is -2.
Therefore, these charges will cancel out each other as we write the formula in simplest crisscross method.
Also, the numbers in a chemical formula display the total number of atoms attached with each other or central atom.
For example, in 
there are two chlorine atoms attached to one calcium atom.
Therefore, 
denotes one sulfur atom is attached to magnesium atom. Hence, we do not write the formula of magnesium sulfide as because this shows two magnesium atoms are attached to two sulfur atoms which is not true.
3. Conducts electricity in aqueous solution.
Answer:
The correct answer is 8.79 × 10⁻² M.
Explanation:
Based on the given information, the mass of NaI given is 4.11 grams. The molecular mass of NaI is 149.89 gram per mole. The moles of NaI can be determined by using the formula,
No. of moles of NaI = Weight of NaI/ Molecular mass
= 4.11 / 149.89
= 0.027420
The vol. of the solution given is 312 ml or 0.312 L
The molarity can be determined by using the formula,
Molarity = No. of moles/ Volume of the solution in L
= 0.027420/0.312
= 0.0879 M or 8.79 × 10⁻² M
Main advantages of DDT are the insecticide property and the knoledge about its chemical synthesis.
Explanation:
At that time in 1939 it was discovered that DDT have insecticide properties. It is a useful property because it allows inhibition of insects populations in large areas. Killing insects will reduce the diseases transmitted by them as typhus and malaria. More over you prevent the destruction of the agricultural crops by the harmful insects.
However the synthesis of the molecule was known way back in 1874. From that time it was plenty of time in which chemistry knowledge evolved so the synthesis at kilograms scale was implemented. High quantities of DDT molecule become available for the market so that in 1945 was available as agricultural insecticide.
It was discovered that DDT have bad effects for human health and also over time some insects developed resistance and their were not affected anymore by the molecule.
You may find the chemical structure of DDT in the attached figure.
Lean more:
about DDT
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