Calculate the number of molecules present in 2.24 $\text{dm}^3$ of carbon dioxide at STP ?

What is uncertainty in velocity of an electron if uncertainty in measurement of position is 50 pm ? $(m_e = 9.1 \times 10^{-31}\text{kg},\ h = 6.63 \times 10^{-34}\text{Js},\ \pi = 3.142)$

Which of the following elements belongs to group 2 and sixth period of periodic table?

Identify a molecule having highest dipole moment from following.