Test: Mole Concept and Stoichiometry - Class 10 MCQ

Helium (He) is an example of a monatomic gas, meaning it consists of single atoms. Monatomic gases are typically noble gases and do not readily form molecules.

Avogadro's Law is primarily used to determine the molecular formula of gases. By knowing the volume and number of moles, chemists can derive the molecular composition of gaseous substances.

The relative molecular mass of a gas or vapor is calculated using the formula Relative Molecular Mass = 2 × VD, where VD is the relative vapor density. This relationship helps in understanding the properties of gases in various conditions.

Ozone (O₃) is classified as a triatomic gas since it consists of three oxygen atoms. Triatomic molecules often exhibit unique properties compared to diatomic or monatomic gases.

The gram molecular mass of a substance is numerically equal to the gram molar volume at standard temperature and pressure (STP), which is 22.4 liters for one mole of an ideal gas.

Boyle's Law states that the volume of a given mass of gas is inversely proportional to its pressure when the temperature is constant. This means that as pressure increases, volume decreases, and vice versa, illustrating the relationship between these two variables.

The empirical formula represents the simplest whole number ratio of the different elements in a compound. It may not reflect the exact number of atoms in a molecule but gives a basic understanding of its composition.

Standard pressure is defined as 760 mm Hg, which is equivalent to 1 atmosphere (atm). This standard is widely used in scientific calculations involving gases.

The standard temperature is 273 K, which corresponds to 0°C. This temperature is often used as a reference point in gas law calculations to ensure consistency across various scientific applications.

The molecular formula P4 indicates that phosphorus exists as a tetratomic molecule, meaning it is composed of four identical atoms. This form is commonly found in certain allotropes of phosphorus, such as white phosphorus.

The gram atomic mass refers to the mass of one mole of atoms of an element expressed in grams. It is numerically equivalent to the atomic mass of the element measured in atomic mass units (amu).

Charles's Law states that the volume of a given mass of gas is directly proportional to its absolute temperature when the pressure is held constant. This means that as temperature increases, volume also increases.

Gay-Lussac's law of combining volumes indicates that when gases react, they do so in simple whole number ratios by volume, provided that the gases are at the same temperature and pressure. This principle underlines the stoichiometry of gas reactions.

If a gas has a relative vapor density (VD) of 1, its relative molecular mass is calculated as 2 × VD, resulting in a relative molecular mass of 2. This means it is lighter than air, which has a relative molecular mass of approximately 29.

Ozone is represented by the molecular formula O₃, indicating that it is composed of three oxygen atoms. Ozone plays a critical role in the Earth's atmosphere, particularly in absorbing harmful ultraviolet radiation.

Chlorine gas (Cl₂) is a diatomic gas, meaning it is composed of two identical atoms. Diatomic gases are common and include other examples such as H₂ and O₂.

Avogadro's Number, approximately 6.022 × 10²³, signifies the number of particles (atoms, molecules, ions) in one mole of a substance. This fundamental constant allows chemists to relate macroscopic quantities of materials to the atomic and molecular scale.

The empirical formula mass is calculated by summing the atomic masses of the elements as represented in the empirical formula. This value is essential for stoichiometric calculations in chemical reactions.

The empirical formula is determined by the simplest whole number ratio of the elements in the compound. In this case, 40% carbon and 60% oxygen simplifies to the ratio of 1:1, giving the empirical formula CO.

Avogadro's Law states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules. This law is crucial for determining the atomicity of gases, which refers to the number of atoms in a molecule.