Tag: quantitative chemistry

Quizzes (10) Questions (111)

Questions Related to quantitative chemistry

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

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

  1. 66.7 gm

  2. 252 gm

  3. 112 gm

  4. 168 gm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The balanced reaction is 2H3PO4 + 3Mg(OH)2 -> Mg3(PO4)2 + 6H2O. Calculate the moles of Mg(OH)2 (100/58.3), then use the stoichiometric ratio to find the required moles of H3PO4, and finally convert to grams.

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

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

  1. $44.4$
  2. $44.8$
  3. $44.1$
  4. $55.8$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

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

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

  1. $10$ gm moles
  2. $5$ gm moles
  3. $1$ gm mole
  4. $0.5$ gm mole
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $=\dfrac{3.011\times 10^{24}}{6.022\times 10^{23}}=5\ gm\ mole$

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

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

  1. (a) 249 (b) 249

  2. (a) 124.5 (b) 124.5

  3. (a) 249 (b) 124.5

  4. (a) 124.5 (b) 249
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $=\dfrac { 249 }{ 2 } =124.5$

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

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:

  1. 225 g

  2. 250 g

  3. 300 g

  4. 150 g
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Given,
Concentration of $NaOH=0.1 N$
Volume$=10\,mL$
Mass of Dibasic acid$=3g$
Volume$=25\,mL$
Using,
$n _{1}M _{1}V _{1}=n _{2}M _{2}V _{2}$
$n _{2}=2$
$\Rightarrow 1\times 0.1\times 10=2\times25\times\cfrac{3}{M}$
$\Rightarrow M=\cfrac{2\times 25\times 3}{10\times 0.1}$
$\Rightarrow M=150\,g$
Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

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

  1. $M$
  2. $2M$
  3. $3M$
  4. $4M$
Reveal answer Fill a bubble to check yourself
D Correct answer
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$=4\,Mg/mol$
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. Methane

  2. Carbon monoxide

  3. Ethane

  4. Oxygen
Reveal answer Fill a bubble to check yourself
A Correct answer
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)

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. Boyle's Law

  2. Charles's Law

  3. Avogadro's Principle

  4. Ideal Gas Law
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. $11.2L$
  2. $0.0224L$
  3. $0.0112L$
  4. $22.4L$
Reveal answer Fill a bubble to check yourself
C Correct answer
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 $\Rightarrow (X)$ 
$\Rightarrow X = \dfrac{22.4 \times 3 \times 10^{20}}{6.02 \times 10^{23}} = 0.0112\space L$

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. Boyle's law

  2. Charle's law

  3. Avogardro's law

  4. ideal gas law

  5. Dalton's law
Reveal answer Fill a bubble to check yourself
C Correct answer
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.