Tag: quantitative chemistry

Questions Related to quantitative chemistry

How many grams of phosphoric acid would be needed to neutralize $100$ gm of magnesium hydroxide? (Molecular weight of $H _3PO _4=98$ and $Mg(OH) _2=58.3 gm$)

chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

  1. 66.7 gm

  2. 252 gm

  3. 112 gm

  4. 168 gm

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Correct Option: C

The weight of $1$ litre of a glass at STP is $2$ grams, its molecular weight is:

chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

  1. $44.4$

  2. $44.8$

  3. $44.1$

  4. $55.8$

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Correct Option: B
Explanation:

$At\quad STP,\quad volume\quad of\quad 1\quad mole\quad gas\quad =\quad 22.4\quad L\ Mass\quad of\quad 1L\quad gas\quad =\quad 2g\ Mass\quad of\quad 22.4L\quad gas\quad =\quad 2\times 22.4\quad =\quad 44.8\ So,\quad molecular\quad weight\quad of\quad gas\quad =\quad 44.8\ So,\quad correct\quad answer\quad is\quad option\quad B.$

The number of gram-molecules of oxygen in $6.022\times 10^{24}$ molecules of $CO$ is:

chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

  1. $10$ gm moles

  2. $5$ gm moles

  3. $1$ gm mole

  4. $0.5$ gm mole

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Correct Option: B
Explanation:

Number of oxygen atoms = Number of $CO$ molecules$=6.022\times 10^{24}$

Number of oxygen molecule $=\dfrac12\times$  Number of oxygen atoms $=3.011\times 10^{24}$
Number of g-molecule of $O _2$ molecules $=\dfrac{3.011\times 10^{24}}{6.022\times 10^{23}}=5\ gm\ mole$

The molar mass of $CuSO _4.5H _2O$ is 249. Its equivalent mass in the reaction (a) and (b) would be:
(a) Reaction $CuSO _4 + KI \rightarrow$ product
(b) Electrolysis of $CuSO _4$ solution

chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

  1. (a) 249 (b) 249

  2. (a) 124.5 (b) 124.5

  3. (a) 249 (b) 124.5

  4. (a) 124.5 (b) 249

Show answer
Correct Option: B
Explanation:

In water, ${ CuSO } _{ 4 }\cdot 5{ H } _{ 2 }O$ dissociates into ${ Cu }^{ 2+ }$ & ${ SO } _{ 4 }^{ 2- }$. The ions are doubly charged. Hence half as much is needed to react with a compound that dissociates into singly charged species.

(a) Reaction of ${ CuSO } _{ 4 }+KI\longrightarrow $ products.
     Eq. wt of ${ CuSO } _{ 4 }=249/2=124.5$
(b) Electrolysis of ${ CuSO } _{ 4 }$
     At Cathode ${ \underset { +2 }{ Cu }  }^{ 2+ }+{ 2e }^{ - }\longrightarrow \underset { 0 }{ Cu } $
$\therefore$   Charge in oxidation state $=2=n-$factor
$\therefore$   Eq. wt $=\dfrac { 249 }{ 2 } =124.5$

10 ml of 0.1 M solution sodium hydroxide is completely neutralised by 25 ml of 3 gram of dibasic acid in one solution the molecular weight of acid is:

chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

  1. 225 g

  2. 250 g

  3. 300 g

  4. 150 g

Show answer
Correct Option: D
Explanation:
Given,
Concentration of $NaOH=0.1 N$
Volume$=10\,mL$
Mass of Dibasic acid$=3g$
Volume$=25\,mL$
Using,
$n _{1}M _{1}V _{1}=n _{2}M _{2}V _{2}$
$n _{2}=2$
$\Rightarrow 1\times 0.1\times 10=2\times25\times\cfrac{3}{M}$
$\Rightarrow M=\cfrac{2\times 25\times 3}{10\times 0.1}$
$\Rightarrow M=150\,g$

M g of a substance when vaporised occupy a volume of 5.6 litre at NTP. The molecular mass of the substance will be: 

chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

  1. $M$

  2. $2M$

  3. $3M$

  4. $4M$

Show answer
Correct Option: D
Explanation:
Given,
$Mg$ of substance occupy volume$=5.6\,litre $ at NTP.
At NTP,
1 mol occupy 22.4 litre of volume.
5.6 litre$=Mg$
22.4 litres$=4\,Mg$ of substance.
So, Molecular mass of gas$=4\,Mg/mol$

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

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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.