Which of the phosphorus oxoacids can create a silver mirror from $AgNO_3$ solution?

Which of the following represents laughing gas?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$ : $PH_3$ has lower boiling point than $NH_3$.
Reason $(R)$ : In liquid state $NH_3$ molecules are associated through van der Waals forces,but $PH_3$ molecules are associated through hydrogen bonding.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following reactions gives nitrogen $(II)$ oxide $(NO)$ as one of the products?

Which of the following is an ionic compound?

Which of the following oxides of nitrogen is not a common pollutant in the atmosphere?