How is concentrated $H_2SO_4$ diluted?

Which of the following aqueous solutions is neutral?

$100 \ mL$,$1 \ M$ $H_2SO_4$ solution of density $1.5 \ g/mL$ is mixed with $400 \ mL$ of water,resulting in a diluted solution of density $1.25 \ g/mL$. Find the molarity of the final diluted solution. (Density of water $= 1 \ g/mL$)

When metallic copper comes in contact with moisture,a green powdery/pasty coating can be seen over it. This is chemically known as

The number of electrons in one molecule of urea $(NH_2CONH_2)$ is

$A$ gas has a density of $2.68 \ g/L$ at $STP$. Identify the gas.