5. Molecules and Compounds
Law of Definite Proportions
Multiple Choice
A 7.74 g sample of HCN is found to contain 0.287 g of H and 4.01 g N. Find the mass of carbon in a sample of HCN with a mass of 3.43 g.
A
1.28 g C
B
1.53 g C
C
1.70 g C
D
2.01 g C
Verified step by step guidance1
Determine the mass of carbon in the original 7.74 g sample of HCN by subtracting the masses of hydrogen and nitrogen from the total mass: Mass of carbon = Total mass - Mass of hydrogen - Mass of nitrogen.
Calculate the mass of carbon in the original sample: Mass of carbon = 7.74 g - 0.287 g - 4.01 g.
Find the mass fraction of carbon in the original sample by dividing the mass of carbon by the total mass of the original sample: Mass fraction of carbon = Mass of carbon / 7.74 g.
Use the mass fraction of carbon to find the mass of carbon in the new 3.43 g sample of HCN: Mass of carbon in new sample = Mass fraction of carbon * 3.43 g.
Verify the calculation by ensuring that the sum of the masses of hydrogen, carbon, and nitrogen in the new sample equals the total mass of the new sample (3.43 g).
