Tag: chemistry

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Questions Related to chemistry

Multiple choice chemistry substances in the surroundings - their states and properties elastic behaviour of solids elastic and plastic substances properties of substances

Which one of the following substance possesses the highest elasticity?

  1. rubber

  2. glass

  3. steel

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

Modulus of elasticity gives the idea of elasticity. For above materials, values of E are:
Glass: $50-90 GPa$
Rubber:$ 0.01-0.1 GPa$
Steel:$ 200 GPa$
Copper: $117 GPa$

Multiple choice chemistry substances in the surroundings - their states and properties elastic behaviour of solids elastic and plastic substances properties of substances

Pick up the correct statement:

  1. Cubic crystals exhibit isotropic nature with respect to therma expansion

  2. Anisotropic solids expand in one direction and contract in perpendicular direction

  3. Many of the crystals are anisotropic solids

  4. Rock salt crystal exhibits isotropic nature with respect to thermal expansion
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Crystals are typically anisotropic, meaning their physical properties (like thermal expansion) vary depending on the direction of measurement. Many crystals exhibit this property.

Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

Which of the following molecules specie has the minimum number of lone pairs ? 

  1. $ X _eF _4 $
  2. $ BF^- _4 $
  3. $ ICI _3 $
  4. $ BeF _2 $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

BeF2 has a linear structure with no lone pairs on the central Beryllium atom. XeF4 has 2, BF4- has 0 (but is an ion), and ICl3 has 2. However, BeF2 is the neutral molecule with zero lone pairs on the central atom.

Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

A quantity of $2.0\ g$ of a triatomic gaseous element was found to occupy a volume of $448\ ml$ at $76\ cm$ of $Hg$ and $273\ K$.

The mass of its each atom is _______________.

  1. $100\ amu$
  2. $5.53\times 10^{-23}\ g$
  3. $33.3\ g$
  4. $5.53\ amu$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Given that
$P=76\ cm$ of $Hg =1\ atm$
$V=448\ ml=0.448\ L$
$T=273\ K$

Now,
$PV=nRT$

$n=\dfrac{PV}{RT}=\dfrac{1\times 0.448}{0.082\times 273}=0.02\ moles$

No. of moles $=\dfrac{mass}{molar\ mass}$

Molar mass $=\dfrac{mass}{mole}$

$3\times$ atomic mass $=\dfrac{2}{0.02}$

Atomic mass $=33.3\ g$

$\therefore$ mass of $1\ atom=\dfrac{33.3}{6.022\times 10^{23}}=5.53\times 10^{-23}\ g$
Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

Which of the following gas molecule has the longest mean free path at the same pressure and temperature?

  1. $H _2$
  2. $N _2$
  3. $O _2$
  4. $Cl _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Mean free path is inversely proportional to the collision cross-section. Smaller molecules like H2 have a smaller cross-section, leading to a longer mean free path compared to larger molecules like N2, O2, or Cl2.

Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

Two gases X and Y have their molecular speed in ratio of $3:1$ at certain temperature. The ratio of their molecular masses $M _x:M _y$ is?

  1. $1:3$
  2. $3:1$
  3. $1:9$
  4. $9:1$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Molecular speed v is proportional to 1/sqrt(M). If v_x/v_y = 3/1, then sqrt(M_y/M_x) = 3/1, so M_y/M_x = 9/1. Thus, M_x/M_y = 1/9.

Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

A gaseous mixture of three gases A, B and C has a pressure of $10$ atm. The total number of moles of all the gases is $10$. If the partial pressures of A and B are $3.0$ and $1.0$ atm, respectively, and if C has molecular mass of $2.0$, what is the mass of C, in g, present in the mixture?

  1. $6$
  2. $8$
  3. $12$
  4. $3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Dalton's law of partial pressures, the partial pressure of a gas is proportional to its mole fraction. The mole fraction of gas C is calculated from total moles (10) and total pressure (10 atm), where the sum of partial pressures of A and B is 3.0 + 1.0 = 4.0 atm, leaving the partial pressure of C as 10 - 4 = 6 atm. Thus, the moles of C equal (6/10) * 10 = 6 moles. With a molecular mass of 2.0 g/mol, the mass of C is 6 moles * 2.0 g/mol = 12 g.