Tag: chemistry

Questions Related to chemistry

The rate constant for the reaction is $2 10^{-4} s^{-1}.$ The reaction is :

chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

  1. First order

  2. Second order

  3. Third order

  4. Zero order

Show answer
Correct Option: A

For a second-order reaction of the type rate=$k[A]^2$ the plot of $\dfrac{1}{[A] _1}$ versus t is linear with a: 

chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

  1. positive slope and zero intercept

  2. positive slope and non-zero intercept

  3. negative slope and zero intercept

  4. negative slope and non-zero intercept

Show answer
Correct Option: B
Explanation:

Given that for a second order reaction

$Rate= K[A]^2$

We know that rate of the reaction is decrease in the concentration of the reactant with respect to time.

$Rate= \cfrac {-d[A]}{dt}$
$\Rightarrow$ $\cfrac {-d[A]}{dt}=K[A]^2$
$\Rightarrow \cfrac {-d[A]}{[A]^2}=+Kdt$

Integrating both sides we have:-
$\Rightarrow -\int \cfrac {d[A]}{[A]^2}=+\int Kdt$
$\Rightarrow - \left[\cfrac {-1}{[A]}\right]=+Kt+C$
$\Rightarrow Kt+C= \cfrac {1}{[A]}$      $- (i)$

Now, from the equation $(i)$ we can see that graph of $\cfrac {1}{[A]}$ $V/s$ $t$ has a positive slope $K$ and non-zero intercept $C$.

22.4 litres of a gas at STP weighs 16 g. Identify the gas.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Methane

  2. Carbon monoxide

  3. Ethane

  4. Oxygen

Show answer
Correct Option: A
Explanation:

At STP,  1 mole of gas occupies $22.4l$.

Given gas occupies $22.4l$ at STP and has weight 16 g.
So molecular weight of gas is 16. 
Thus Ans: Methane (Mol. weight of methane is 16)

All gases have the same number of moles in the same volume at constant temperature and pressure.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Boyle's Law

  2. Charles's Law

  3. Avogadro's Principle

  4. Ideal Gas Law

Show answer
Correct Option: C
Explanation:

According to the Avogadro's principal, every gas have the same number of moles in the same volume at constant temperature and pressure.

What is the volume of $3.0\times {10}^{20}$ molecules of $HCl (g)$?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $11.2L$

  2. $0.0224L$

  3. $0.0112L$

  4. $22.4L$

Show answer
Correct Option: C
Explanation:

$1 \space Mole$ of gas at STP occupy $22.4 \space Litres$ of gas

As, $1 \space Mole = 6.02 \times 10^{23}$ molecules $\Rightarrow 22.4 Litres$ 
$3.0 \times 10^{20}$ molecules $\Rightarrow (X)$ 
$\Rightarrow X = \dfrac{22.4 \times 3 \times 10^{20}}{6.02 \times 10^{23}} = 0.0112\space L$

All gases have the same number of moles in the same volume at constant T and P is stated by :

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Boyle's law

  2. Charle's law

  3. Avogardro's law

  4. ideal gas law

  5. Dalton's law

Show answer
Correct Option: C
Explanation:

Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules". For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.

Which statement is linked with the idea that two identical containers filled with different gases will contain the same number of particles?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Mosely

  2. Avagadro

  3. Dalton

  4. Mendeleev

Show answer
Correct Option: B
Explanation:

Avagadro stated that when two identical containers are filled with different gases at same pressure and temperature, they contain same number of particles.

So, the statement is linked with Avagadro.

What is the volume occupied by 17.75 g of $Cl _2$ at STP?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $5.6l$

  2. $22.4l$

  3. $11.2l$

  4. $2.8l$

Show answer
Correct Option: A
Explanation:

In order to solve this problem, we would use the ideal gas law formula PV = nRT 

at STP standard temp and pressure is 1 atm and 273k

we have 

P = 1atm, n = $\dfrac{17.75}{70.90}$ mole = 0.250, R = $0.0821$ $atm*L/mol*K$ , T=$273K$

V = $\dfrac {nRT}{P}$

= $0.250\times 0.0821\times 273$

= $5.6L$

answer is A


Which term describes the mass of $6.022\times { 10 }^{ 23 }$ representative particles?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Molar mass

  2. Avogadro's number

  3. Empirical formula

  4. Molecular formula

Show answer
Correct Option: A
Explanation:

Molar mass of a compound describes the total mass of $6.023 \times 10^{23}$ atoms or particles of the compound.

Ex: Molar mass of $H _2 = 2\space g$

A sample of ammonia has a mass of $51.1g$. How many molecules are in this sample?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $1.8\times {10}^{23}$ molecules

  2. $3.6\times {10}^{23}$ molecules

  3. $9.1\times {10}^{23}$ molecules

  4. $1.8\times {10}^{24}$ molecules

Show answer
Correct Option: D
Explanation:
given mass of ammonia is 51.1g
in this number of moles =  $\dfrac{51.1}{17.031}$ = 18
Now in a mole, there are Na molecules, this is known $6.023\times 10^{23}$ 
since 1 mol = $6.023\times 10^{23}$ 

thus,

18 mol = $18\times 6.023\times 10^{23}$  = $1.8\times 10^{24}$