What is the part of the plant used in tissue culture called?

The $pK_a$ of a weak acid is $4.8$. What should be the ratio of $[Acid]/[Salt]$ of a buffer if $pH = 5.8$ is required?

The products formed when diethyl ether is reacted with cold $HI$ are

In the $Al_{2}Cl_{6}$ dimer,which of the following statements is true regarding the $Al-Cl$ bonds?

The total number of nitrogenous bases in the human genome is estimated to be about

If $a, b$ and $c$ are three non-coplanar vectors and $p, q$ and $r$ are vectors defined by $p=\frac{b \times c}{[a b c]}, q=\frac{c \times a}{[a b c]}$ and $r=\frac{a \times b}{[a b c]}$,then the value of $(a+b) \cdot p+(b+c) \cdot q+(c+a) \cdot r$ is equal to