What weight of ferrous ammonium sulphate is needed to prepare $100 \, mL$ of $0.1 \, N$ solution? (mol. wt. $392$)

The ammonia evolved from $2 \ g$ of a compound in Kjeldahl's estimation of nitrogen neutralises $10 \ mL$ of $2 \ M \ H_2SO_4$ solution. The weight percentage of nitrogen in the compound is

$100 \ mL$ of aqueous solution of $0.05 \ M$ $Cu^{2+}$ is added to $1 \ L$ of $0.1 \ M$ $KI$ solution. The resultant solution was titrated with $0.01 \ M$ $Na_2S_2O_3$ solution using starch indicator till blue color disappeared. What is the volume (in $mL$) of $Na_2S_2O_3$ used?

Estimation of $CO$ is done by using:

The disodium salt of ethylene diamine tetraacetic acid can be used to estimate the following ion$(s)$ in an aqueous solution:

$A$ $2.0 \, g$ sample containing $MnO_2$ is treated with $HCl$ liberating $Cl_2$. The $Cl_2$ gas is passed into a solution of $KI$ and $60.0 \, mL$ of $0.1 \, M \, Na_2S_2O_3$ is required to titrate the liberated iodine. The percentage of $MnO_2$ in the sample is $.....$ (Nearest integer).
[Atomic masses (in $u$): $Mn = 55, Cl = 35.5, O = 16, I = 127, Na = 23, K = 39, S = 32$]