Exams

Tina

Among the given options Brass is not a compound. Since it is an alloy, it is a mixture. It is a mixture of copper and zinc.

The smallest part of a compound is called a molecule. It has a unique composition that is always the same.

Compound is a substance that consists of two or more elements. 

   1) SO2                  2) CH2Cl2                3) PCl3

How to check the given molecules are polar or non polar :

If the electronegativity of the two bonded atoms are different then the bond is polar. Although, some molecules contain polar bonds, the molecule may be non-polar. If the polarity of all the bonds present in the molecule are cancel each other then molecule is non-polar.

In the given options,

SO2  is polar because the dipole moments on the O do not cancel.

PCl3  is polar because the P-Cl bonds do not cancel out.

CH2Cl2  polar because the C-Cl bonds do not cancel.

Hence, in brief, Polar molecules are molecules with net dipole due to the presence of partial positive and partial negative charge.

For example, water is a polar molecule that has partial positive and partial negative charge on it. CO2 is a non polar compound.

Therefore, all the given options SO2, CH2Cl2 and PCl3 are Polar molecules.

Sony and her brother's age sum is 31
Let Sony's mother's age be 'x'.
Now the conditions given for both of their ages related to their mom is
1/5(x-15) + 3/5(x-10) = 31
x-15 + 3x-30 = 155
4x-45 = 155
4x = 200
x = 50
So, Mother's age = 50.

Cross verification : 15 years ago age = 35 => Sony age = 7
10 years ago age = 40 => bro age = 24

Sum = 24 + 7 = 31.