Question

A vessel contains 1.6 g of dioxygen at STP (273.15 K, 1 atm pressure). The gas is now transferred to another vessel at constant temperature, where pressure becomes half of the original pressure. Calculate (i) volume of the new vessel. (ii) number of molecules of dioxygen.

The mass of one mole of a substance in grams is called its molar mass. the molar mass in grams is numerically equal to atomic molecular/formula mass in u. An empirical formula represents the simplest whole number ratio of various atoms present in a compound, whereas, the molecular formula shows the exact number of different types of atoms present in a molecule of a compound. If the mass per cent of various elements present in a compound is known, its empirical formula can be determined. Molecular formula can further be obtained if the molar mass is known. Many a time, reactions are carried out with the Amounts of reactants that are different than The amounts as required by a balanced chemical reaction. The reactant which is present in the least amount gets consumed after sometime and after that further reaction does not take place whatever be the amount of the other reactant. Hence, the reactant, which gets consumed first, limits the amount of product formed and is, therefore, called the limiting reagent.

Quantitative measurement of properties is required for scientific investigation. Earlier, two different systems of measurement, i.e., the English System and the Metric System were being used in different parts of the world. The metric system, which originated in France in late eighteenth century. The SI system has seven base units. | Base Physical Quantities | Unit | |--------------------------|------| | 1. Length | Metre – m | | 2. Mass | Kilogram – kg | | 3. Time | Second – s | | 4. Electric current | Ampere- A | | 5. Thermodynamic Temperature | Kelvin – K | | 6. Amount of substance | Mole – mol | | 7. Luminous intensity | Candela- cd | Mass of a substance is the amount of matter present in it, while weight is the force exerted by gravity on an object. Density of a substance is its amount of mass per unit volume. The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 10²³ elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit per mol and is called the Avogadro number. There are three common scales to measure temperature — °C (degree celsius), °F (degree fahrenheit) and K (kelvin). The temperatures on two scales are related to each other by the following relationship: °F = 9/5 (°C) + 32 The kelvin scale is related to celsius scale as follows: K = °C + 273.15

Calculate (a) the no of atoms in 3 mol of NH3 (b) the no. of molecules in 1ml of CO2 at STP.