A teacher enters a classroom from front door while a student from back door. There are 13 equidistant rows of benches in the classroom. The teacher releases $N_{2} O$ , the laughing gas, from the first bench while the student releases the weeping gas $(C_{6} H_{11} O B r)$ from the last bench. At which row will the students starts laughing and weeping simultaneously?

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is B 9
As we know that,
$r \propto \frac{1}{M}$
Let $r_{1}$ and $r_{2}$ be the row from front and last respectively at which the students start laughing and weping simultaneously and $M_{1}$ and $M_{2}$ be the molar masses of gas released from front and back side respectively.
$\Rightarrow \frac{r_{1}}{r_{2}} = \sqrt{\frac{M_{2}}{M_{1}}}$
Moleculrr weight of laughing gas $(N O_{2}) = 44 g$
Molecular weight of weeping gas $(C_{6} H_{11} O B r) = 179 g$
Given that the lughing gas i released from the front side while the weeping gas is released from the back side.
$∴ \frac{r_{1}}{r_{2}} = \sqrt{\frac{M_{w}}{M_{l}}}$
$\Rightarrow \frac{r_{1}}{r_{2}} = \sqrt{\frac{179}{44}} \approx 2$
Let $x$ be the row from the front where students start laughing and weeping simultaneously, i.e., $r_{1} = x$ .
Given that $r_{1} + r_{2} = 13$
$∴ r_{2} = 13 - x$
$∴ \frac{x}{(13 - x)} = 2$
$\Rightarrow x = 26 - 2 x$
$\Rightarrow x = \frac{26}{3} = 8.66 \approx 9$
Hence at $9^{t h}$ row, student will start laughing and weeping simultaneously.
Hence the required answer is $(C) 9$ .

Suggest Corrections

Similar questions

Q. A teacher enters a classroom from front door while a student from back door. There are 13 equidistant rows of benches in the classroom. The teacher releases

N_{2} O

, the laughing gas, from the first bench while the student releases the tear gas

(C_{10} H_{5} C l N_{2})

from the last bench. At which row will the students starts laughing and weeping simultaneously

Q. A 100 feet long classroom maintains seating row after every 10 feet and has doors on both front and back sides. A laughing gas

(N_{2} O)

cylinder and a tear gas (methane) cylinder were opened simultaneously at the front and the back door respectively. Assuming both the gases were present at the same temperature and pressure and the cylinder has similar valve dimensions. If the student of

n^{t h}

row, from the front, simultaneously weeps and laughs, the value of n is .

A cinema hall has equidistant rows 1 m apart. The length of the cinema hall is 287 m and it has 287 rows. From one side of the cinema hall, laughing gas(N₂O) is released and from the other side, tear gas(C₆H₅COCH₂CI) is released. In which rows, spectators will be laughing and weeping simultaneously?

A cinema hall has equidistant rows $1$ m apart. The length of the cinema hall is $287$ m and it has $287$ rows. From one side of the cinema hall, laughing gas $(N_{2} O)$ is released and from the other side, tear gas $(C_{6} H_{5} C O C H_{2} C l)$ is released. In which rows, spectators will be laughing and weeping simultaneously?

Q. A teacher stands in front of the door of a classroom, and only one row of students sitting at their desks can see the teacher. The teacher speaks from the same location, and all the students in the classroom (five rows) are able to hear.
Since both the light waves and the sound waves from the teacher pass through the door, why can all students hear the teacher but not see the teacher?

Join BYJU'S Learning Program