Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction.

If $\vec{a} = \hat{i} - \hat{j} - \hat{k}$ and $\vec{b} = \lambda\hat{i} - 3\hat{j} + \hat{k}$ and the orthogonal projection of $\vec{b}$ on $\vec{a}$ is $\frac{4}{3}(\hat{i} - \hat{j} - \hat{k})$,then $\lambda$ is equal to:

$Ni$ anode is used in the electrolytic extraction of

In the reaction,$2SO_2 + O_2 \xrightarrow[As_2O_3]{Pt} 2SO_3$,$As_2O_3$ acts as:

Which of the following substances has the highest melting point?

The time taken for a calorimeter containing $75 \ g$ of water at $62^{\circ} C$ to cool to $58^{\circ} C$ is $9 \ \text{minutes}$. When the calorimeter contains $105 \ g$ of water, it takes $12 \ \text{minutes}$ to cool from $62^{\circ} C$ to $58^{\circ} C$. The water equivalent of the calorimeter is: (in $g$)