When $MgCl_2 \cdot 6H_2O$ is strongly heated,then it forms

$6 \Omega$ and $12 \Omega$ resistors are connected in parallel. This combination is connected in series with a $10 \text{ V}$ battery and a $6 \Omega$ resistor. What is the potential difference between the terminals of the $12 \Omega$ resistor (in $text{ V}$)?

Which of the following monosaccharides is a pentose?

Which of the following compounds will be most easily attacked by an electrophile?

The major product of the following reaction is:

Evaluate the sum: $\sum\limits_{k = 1}^n {\frac{1}{{{{\log }_{{2^k}}}(a)}}}$