Some Basic Concepts of Chemistry quiz

The number of significant figures in 0.00250 is:

The SI unit of amount of substance is:

The molar mass of H2SO4 is:

Which law states that a compound always contains the same elements in the same proportion by mass?

The number of atoms in 1 mole of oxygen gas (O2) is:

Which concentration unit is independent of temperature?

The empirical formula of glucose (C6H12O6) is:

1 amu (unified mass) is equal to:

Which of the following is a mixture?

The law of conservation of mass was given by:

What is the difference between precision and accuracy? (2 marks)

What is dimensional analysis? Convert 3 m into cm using it. (2 marks)

State Avogadro's law. (2 marks)

Why is molality preferred over molarity in some studies? (2 marks)

What is the formula mass of NaCl? (2 marks)

Why is it necessary to balance a chemical equation before calculations? (2 marks)

What is mole fraction? (2 marks)

Distinguish between homogeneous and heterogeneous mixtures. (2 marks)

What is meant by the average atomic mass of chlorine? (2 marks)

How do you calculate the number of moles from the mass of a substance? (2 marks)

Calculate the molarity of a solution containing 4 g of NaOH dissolved in 250 mL of solution (NaOH = 40 g/mol). (3 marks)

46 g of ethanol is mixed with 90 g of water. Calculate the mole fraction of ethanol (C2H5OH = 46 g/mol, H2O = 18 g/mol). (3 marks)

Calculate the mass of CO2 produced when 16 g of methane burns completely in oxygen. (3 marks)

Chlorine has two isotopes, 35Cl (75.77%) and 37Cl (24.23%), with masses 34.97 u and 36.97 u. Calculate the average atomic mass. (3 marks)

How much copper can be obtained from 100 g of copper sulphate, CuSO4 (Cu = 63.5, S = 32, O = 16)? (3 marks)

Read the passage and answer the questions. Sodium chloride is formed by the reaction of sodium with chlorine gas. A student found that 23 g of sodium always reacts with 35.5 g of chlorine to give 58.5 g of sodium chloride, whatever the source of sodium and chlorine. (i) Which law is illustrated by the constant ratio? (ii) Which law is illustrated by the total mass? (iii) Calculate the moles of NaCl formed. (5 marks)

Read the passage and answer the questions. Gay Lussac observed that when gases combine or are produced in a chemical reaction, they do so in a simple ratio by volume, provided all gases are at the same temperature and pressure. For example, 100 mL of hydrogen combines with 50 mL of oxygen to give 100 mL of water vapour. (i) What is the volume ratio of H2, O2 and water vapour? (ii) How did Avogadro explain this? (iii) What volume of oxygen is needed to react with 300 mL of hydrogen? (5 marks)

Read the passage and answer the questions. A chemistry student weighed a sample several times and got values of 1.95 g, 1.93 g and 1.94 g. The actual mass of the sample was 2.00 g. Another student got 1.94 g, 2.05 g and 2.01 g. (i) Whose results are more precise? (ii) Whose results are more accurate? (iii) Calculate the average of the second student's results. (5 marks)

Read the passage and answer the questions. A reaction mixture contains 2 mol of hydrogen and 2 mol of oxygen: 2H2 + O2 -> 2H2O. The reaction continues until one reactant is used up completely. (i) Which is the limiting reagent? (ii) Calculate the moles of water formed. (iii) Calculate the moles of the excess reactant left. (5 marks)

Read the passage and answer the questions. The concentration of a solution can be expressed in many ways. A solution is made by dissolving 2 g of glucose in 18 g of water. The density of the solution is 1.1 g/mL. (i) Calculate the mass percent of glucose. (ii) Calculate the moles of glucose (180 g/mol). (iii) Calculate the molality of the solution. (5 marks)

Explain the classification of matter with examples. Describe the properties of matter and their measurement using SI units. (6 marks)

Explain the laws of chemical combination with examples. (6 marks)

State Dalton's atomic theory. Explain the concepts of atomic mass, average atomic mass and molecular mass with examples. (6 marks)

Explain the mole concept and molar mass. How are empirical and molecular formulae determined from percentage composition? (6 marks)

Explain stoichiometry and the concept of limiting reagent. Describe the different ways of expressing concentration of solutions with examples. (6 marks)