Determine the number of moles (of molecules or formula units) in each sample. a. 25.5 g NO₂ b. 1.25 kg CO₂ c. 38.2 g KNO₃ d. 155.2 kg Na₂SO₄

검증된 단계별 안내

insert step 1: Identify the molar mass of each compound using the periodic table. For example, calculate the molar mass of NO_2 by adding the atomic masses of nitrogen (N) and oxygen (O).

insert step 2: Convert the mass of each sample to grams if necessary. For instance, convert 1.25 kg of CO_2 to grams by multiplying by 1000.

insert step 3: Use the formula: number of moles = mass of sample (g) / molar mass (g/mol) to calculate the moles for each compound.

insert step 4: Apply the formula to each sample: a. 25.5 g NO_2, b. 1.25 kg CO_2, c. 38.2 g KNO_3, d. 155.2 kg Na_2SO_4.

insert step 5: Ensure all calculations are consistent with significant figures based on the given data.

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주요 개념

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Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all the atoms in a molecule or formula unit. For example, the molar mass of NO2 is approximately 46.01 g/mol, which is essential for converting grams to moles.

Conversion between Mass and Moles

To determine the number of moles from a given mass, the formula used is: moles = mass (g) / molar mass (g/mol). This relationship allows chemists to convert between the mass of a substance and the amount in moles, facilitating stoichiometric calculations in chemical reactions.

Unit Conversion

Unit conversion is the process of converting a quantity expressed in one unit to another unit. In this question, it is necessary to convert kilograms to grams for CO2 and Na2SO4, as the molar mass is typically given in grams per mole. Understanding how to perform these conversions is crucial for accurate calculations.

Determine the number of moles (of molecules or formula units) in each sample. a. 25.5 g NO2 b. 1.25 kg CO2 c. 38.2 g KNO3 d. 155.2 kg Na2SO4