Q. The position of both, an electron and a helium atom is known within $0.1 \,nm$. Further the momentum of the electron is known within $5.0 \times 10^{-26} \,kg \, ms ^{-1}$. The minimum uncertainty in the measurement of momentum of helium atom is.

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A

$50 \, kg \,ms ^{-1}$

B

$5.0 \times 10^{-26} \,kg \, ms ^{-1}$

C

$80 \,kg \,ms ^{-1}$

D

$80 \times 10^{-26} \,kg \,ms ^{-1}$

Solution:

the product of uncertainties in the position and momentum of subatomic particle $=h / 4 \pi$
since $\Delta x$ is same for electron and helium ,so $\Delta p$ must be the same for both particles.

Questions from KCET 2022

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3. Conductivity of a solution is directly proportional to

4. Which of the following is a Lewis acid ?

5. For the reaction $A+B \rightarrow C+D$, it is found that doubling the concentration of $A$ increases rate 4 times and doubling the concentration of B doubles the reaction rate. What is the overall order of the reaction ?

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1. If for a certain reaction $\Delta_{r}H$ is $30\, kJ\, mol^{-1}$ at $450 \,K$, the value of $\Delta_{r}S$ (in $JK^{-1}\, mol^{-1})$ for which the same reaction will be spontaneous at the same temperature is

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2. If $8\,g$ of a non-electrolyte solute is dissolved in $114\, g$ of n-octane to reduce its vapour pressure to $80\%$, the molar mass (in $g \,mol^{-1})$ of the solute is [Given that molar mass of n-octane is $114 \,g\, mol^{-1}]$

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3. An organic compound contains $78 \%$ (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound is: [Atomic wt. of $C$ is $12, H$ is $1$]

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4. At standard conditions, if the change in the enthalpy for the following reaction is $-109 \,kJ\, mol^{-1}$ $H_{2(g)}+Br_{2(g)} \to 2HBr_{(g)}$ Given that bond energy of $H_{2}$ and $Br_{2}$ is $435\,KJ\,mol^{-1}$ and $192\,KJ\,mol^{-1}$ , respectively, what is the bond energy (in $KJ \,mol^{-1})$ of $HBr$ ?

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5. The density of 2 M aqueous solution of NaOH is 1.28 g/cm$^3$. The molality of the solution is
[Given that molecular mass of NaOH = 40 g mol$^{-1}$]

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