Question

when 4.73g of solid was heated, the residue weighed 4.10g 320 cubic centimetre of gas( at RTP) was evolved. calculate the molecular mass of the gas​

Answer 1

48 g/mol

Step-by-step explanation:

Step 1: Calculate the mass of the gas (m)

According to the law of conservation of mass, the mass of the solid before the decomposition must be equal to the sum of the masses of the solid residue and the gas

mSolid = mResidue + mGas

mGas = mSolid - mResidue = 4.73 g - 4.10 g = 0.63 g

Step 2: Convert 320 cm³ to L

We will use the conversion factor 1 L = 1000 cm³.

320 cm³ × 1 L/1000 cm³ = 0.320 L

Step 3: Calculate the moles of gas (n)

The gas is at room temperature (298.15 K) and room pressure (1 atm). We can calculate the moles of gas using the ideal gas equation.

P × V = n × R × T

n = P × V/R × T

n = 1 atm × 0.320 L/(0.0821 atm.L/mol.K) × 298.15 K = 0.0131 mol

Step 4: Calculate the molecular mass of the gas (M)

We will use the following expression.

M = m/n = 0.63 g/0.0131 mol = 48 g/mol