Empirical and molecular formula, percentage composition

36 questions on Empirical and molecular formula, percentage composition from the Mole Concept chapter: 8 NEET level, 15 JEE Main, 13 JEE Advanced. Each one opens with its answer and solution.

• A compound contains 40.0% C, 6.67% H and 53.33% O by mass (C = 12, H = 1, O = 16). Its empirical formula is: NEET level
• The mass percentage of nitrogen in urea, CO(NH2)2, is (H = 1, C = 12, N = 14, O = 16): NEET level
• A hydrocarbon has empirical formula CH and molar mass 78 g mol^-1 (C = 12, H = 1). Its molecular formula is: NEET level
• The mass percentage of water of crystallisation in CuSO4.5H2O is (Cu = 63.5, S = 32, O = 16, H = 1): NEET level
• Complete combustion of 0.74 g of an organic compound containing C, H and O gives 1.76 g of CO2 and 0.90 g of H2O (C = 12, H = 1, O = 16). The empirical formula ... JEE Main level
• On strong heating, 28.6 g of washing soda, Na2CO3.xH2O, leaves a residue of 10.6 g of anhydrous Na2CO3 (Na = 23, C = 12, O = 16, H = 1). The value of x is: JEE Main level
• An oxide of a metal M (atomic mass 56) contains 70% M by mass (O = 16). The formula of the oxide is: JEE Main level
• A hydrocarbon contains 82.76% carbon by mass and has a vapour density of 29 (C = 12, H = 1). Its molecular formula is: JEE Main level
• A fertiliser sample is 90% pure ammonium sulfate, (NH4)2SO4 (H = 1, N = 14, O = 16, S = 32). Calculate the mass of nitrogen (in g) in 250 g of this fertiliser, ... JEE Main level
• A protein contains 0.28% iron by mass (Fe = 56) and each molecule has 4 iron atoms. Its molar mass is xx10^4 g mol^-1. Find x to two decimal places. JEE Main level
• In which of the following pairs do both compounds have the same empirical formula? JEE Main level
• Analysis of 0.89 g of an organic compound containing C, H, N and O gave 1.32 g of CO2, 0.63 g of H2O and 224 mL of N2 at STP (molar volume 22.4 L mol^-1). The m... JEE Advanced level
• Oleum is H2SO4 containing dissolved SO3. A sample labelled 118% oleum means that 100 g of it yields 118 g of pure H2SO4 when diluted with sufficient water (H = ... JEE Advanced level
• A 10.0 g sample consisting of CuSO4.5H2O mixed with a non-volatile inert solid loses 1.80 g on strong heating, all of the loss being the water of crystallisatio... JEE Advanced level
• A mixture of Na2CO3 and NaHCO3 contains 40.0% sodium by mass (Na = 23, C = 12, O = 16, H = 1). What is the mass percentage of Na2CO3 in the mixture? Give one de... JEE Advanced level
• Glucose is C6H12O6 (M = 180) and sucrose is C12H22O11 (M = 342) (H = 1, C = 12, O = 16). Which of the following statements is/are correct? JEE Advanced level
• A hydrocarbon contains 85.71% carbon by mass and has a vapour density of 21 (C = 12, H = 1). Which of the following statements is/are correct? JEE Advanced level
• A sample of 4.88 g of hydrated barium chloride, BaCl2.xH2O, loses 0.72 g of water completely on heating (Ba = 137, Cl = 35.5, O = 16, H = 1). Which of the follo... JEE Advanced level
• The percentage by mass of nitrogen in urea, CO(NH2)2, is closest to (C = 12, H = 1, N = 14, O = 16) NEET level
• A compound contains 40% C, 6.67% H and 53.33% O by mass. Its empirical formula is (C = 12, H = 1, O = 16) NEET level
• A hydrocarbon has empirical formula CH2 and molar mass 84 g mol^-1. Its molecular formula is (C = 12, H = 1) NEET level
• The percentage of water of crystallisation in CuSO4.5H2O is nearly (Cu = 63.5, S = 32, O = 16, H = 1) NEET level
• Complete combustion of 0.74 g of an organic compound containing only C, H and O gives 1.76 g of CO2 and 0.90 g of H2O. The empirical formula is (C = 12, H = 1, ... JEE Main level
• Calculate the mass of iron, in grams, present in 1.00 kg of pure Fe3O4 (Fe = 56, O = 16). Give the answer to the nearest integer. JEE Main level
• A hydrated salt Na2CO3.xH2O contains 62.9% water of crystallisation by mass. Find x to the nearest integer (Na = 23, C = 12, O = 16, H = 1). JEE Main level
• A hydrocarbon contains 92.3% carbon and 7.7% hydrogen by mass and its vapour density is 39. Its molecular formula is (C = 12, H = 1) JEE Main level
• Using C = 12 and H = 1, select the correct statement(s) about the mass percentage of carbon. JEE Main level
• A fertiliser sample contains 40% ammonium sulfate, (NH4)_2SO4, by mass; the remainder has no nitrogen. The mass percentage of nitrogen in the sample is (H = 1, ... JEE Main level
• Haemoglobin contains 0.34% iron by mass. Assuming one Fe atom per molecule, the minimum molar mass of haemoglobin in g mol^-1, to the nearest integer, is (Fe = ... JEE Main level
• Combustion of 1.78 g of an organic compound (C, H, N, O only) gives 2.64 g CO2 and 1.26 g H2O. In a Kjeldahl analysis, all the nitrogen in 0.890 g of the compou... JEE Advanced level
• 20 mL of a gaseous hydrocarbon C_xH_y is mixed with 100 mL of O2 and exploded. After cooling to the initial temperature and pressure (water liquid), the gas vol... JEE Advanced level
• An oxide of a metal M (atomic mass 27) contains 52.94% of M by mass (O = 16). Select the correct statement(s). JEE Advanced level
• A mixture of FeO and Fe2O3 contains 75.0% Fe by mass. The mass percentage of Fe2O3 in the mixture is (Fe = 56, O = 16) JEE Advanced level
• A 5.00 g sample of impure CuSO4.5H2O loses 1.44 g on strong heating (only the water of crystallisation is lost; the impurity is non-volatile and anhydrous). Fin... JEE Advanced level
• A compound contains 29.1% Na, 40.5% S and 30.4% O by mass. Its empirical formula is (Na = 23, S = 32, O = 16) JEE Main level
• Compound X has 40.0% C, 6.67% H and 53.3% O by mass and molar mass 60 g mol^-1. Glucose is C6H12O6 (C = 12, H = 1, O = 16). Select the correct statement(s). JEE Advanced level