Atoms and Molecules quiz

The law of conservation of mass was established by:

The ratio of masses of hydrogen and oxygen in water is:

The atomicity of ozone is:

The symbol of sodium is:

One atomic mass unit is equal to:

The valency of aluminium is:

The formula of calcium chloride is:

The molecular mass of water is:

Which of these is a polyatomic ion?

Which law states that a chemical compound always contains the same elements in a fixed ratio by mass?

Who coined the term atom in Indian philosophy, and what did he call it? (2 marks)

Write the symbols of iron, potassium, copper and gold, and the Latin names from which they come. (2 marks)

What is the difference between a molecule of an element and a molecule of a compound? Give an example of each. (2 marks)

What is the formula unit mass? How is it different from molecular mass? (2 marks)

Write the formula of sodium carbonate and ammonium chloride. (2 marks)

Name the elements present in calcium oxide, hydrogen bromide and potassium sulphate. (2 marks)

Write the names of the compounds Al2(SO4)3, CaCl2, K2SO4 and KNO3. (2 marks)

Which postulate of Dalton's theory was later shown to be incorrect? Why? (2 marks)

What is the role of IUPAC in naming elements? (2 marks)

Give the valency of the ions OH-, NO3-, CO3 2- and PO4 3-. (2 marks)

Calculate the molecular mass of H2SO4 and HNO3. (H = 1 u, N = 14 u, O = 16 u, S = 32 u.) (3 marks)

Calculate the formula unit mass of CaCl2 and CaCO3. (Ca = 40 u, Cl = 35.5 u, C = 12 u, O = 16 u.) (3 marks)

12 g of magnesium burns in 8 g of oxygen to form magnesium oxide. What mass of magnesium oxide is formed? What law is used? (3 marks)

In ammonia, nitrogen and hydrogen combine in the ratio 14 : 3 by mass. What mass of hydrogen is needed to combine completely with 28 g of nitrogen? How much ammonia is formed? (3 marks)

A 0.24 g sample of a compound of boron and oxygen was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Show that the masses agree with the law of conservation of mass and calculate the percentage composition of the compound by mass. (3 marks)

Read the passage and answer the questions. A student mixes a solution of barium chloride with a solution of sodium sulphate in a closed flask placed on a balance. A white precipitate of barium sulphate forms, but the reading on the balance does not change. (i) Which law is verified? (ii) Why was the flask kept closed? (iii) Name the other product formed in the reaction. (5 marks)

Read the passage and answer the questions. Water collected from a river in India and from a lake in Canada was purified and analysed. In both samples, hydrogen and oxygen were present in the ratio 1 : 8 by mass. (i) Which law does this support? (ii) Who stated this law? (iii) If 36 g of pure water is decomposed, find the masses of hydrogen and oxygen obtained. (5 marks)

Read the passage and answer the questions. A chemistry teacher explains that sodium chloride does not consist of molecules but of ions of sodium and chloride arranged in a regular pattern. (i) Write the charges on sodium and chloride ions. (ii) Why do we use formula unit mass for sodium chloride? (iii) Calculate the formula unit mass of NaCl. (Na = 23 u, Cl = 35.5 u.) (5 marks)

Read the passage and answer the questions. Ravi wants to write the formula of aluminium oxide. He knows that aluminium has a valency of 3 and oxygen has a valency of 2. (i) Use the criss-cross method to write the formula. (ii) Calculate its formula unit mass. (Al = 27 u, O = 16 u.) (iii) Is aluminium oxide an ionic compound? Give a reason. (5 marks)

Read the passage and answer the questions. A scientist says that atoms are so small that if you placed about 10 million hydrogen atoms side by side, they would only span about 1 mm. (i) What is the approximate size of an atom expressed in metres? (ii) Why can we not see atoms with our eyes? (iii) Name a modern technique that can produce images of atoms on surfaces. (5 marks)

State and explain the postulates of Dalton's atomic theory. Draw diagrams to show how atoms combine to form molecules of water and carbon dioxide. (6 marks)

Draw a labelled diagram of the experiment to verify the law of conservation of mass. Explain the procedure and observations. (6 marks)

Write the steps to write chemical formulae using valencies. Use the criss-cross method to write the formulae of magnesium chloride, aluminium sulphate, calcium hydroxide and ammonium phosphate. (6 marks)

Draw a chart classifying ions into simple and polyatomic, cations and anions, with two examples each. Explain how they combine to form ionic compounds. (6 marks)

Calculate the molecular masses of C2H5OH, C6H12O6 and HCl and the formula unit mass of Na2CO3. (H = 1 u, C = 12 u, O = 16 u, Na = 23 u, Cl = 35.5 u.) Show all steps. (6 marks)