Which is the correct option for $0.1 \ M$,$500 \ mL$ of $AgCl$?

Suppose you have to determine the percentage of carbon dioxide in a sample of a gas available in a container. Which is the best absorbing material for the carbon dioxide?

Match the scientist's name in List-$A$ with their statement in List-$B$.

List-$A$	List-$B$
$(1)$ Roald Hoffmann	$(A)$ The proportion of the mass of elements in any compound is fixed.
$(2)$ Lavoisier	$(B)$ The smallest indivisible particle of matter is the atom.
$(3)$ Joseph Proust	$(C)$ Chemistry is not the science of $100$ elements.
$(4)$ Dalton	$(D)$ Matter can neither be created nor destroyed.

Which of the following is $NOT$ true for $1 \ g$ of Helium?

$10 \ g$ $NaHCO_{3(s)}$ sample is heated in open to constant weight,the residue is titrated against $0.1 \ M \ HCl$ in presence of phenolphthalein as an indicator,$500 \ mL$ of acid was required to reach end point hence $PERCENT$ purity of sample is $............... \%$.

$A$ mixture of $O_2$ and gas $Y$ (molecular weight $80$) in the mole ratio $a : b$ has a mean molecular weight of $40$. What would be the mean molecular weight if the gases are mixed in the ratio $b : a$ under identical conditions? (The gases are non-reacting)