Grade 12 Chemistry Model Examination

Which of the following branches of chemistry involves separating, identifying and determining the relative amount of a sample of matter?

• Analytical chemistry

• Physical chemistry

• Organic chemistry

• Inorganic chemistry

Which of the following is correct?

• 10L=1dm3

• 1L=10dm3

• 1L=1dm3

• 1L=1m3

A piece of silver metal weighing 160 g is placed in graduated cylinder containing 220 ml of water. The volume of water now reads 240 ml. What is the density of the silver metal?

• 8.5 g/ml

• 8.0 g/ml

• 0.73 g/ml

• 0.35 g/ml

What is the first step of the scientific method?

• Performing an experiment

• Forming a hypothesis

• Predicting the result of an experiment

• Making observation

A student uses a digital balance (± 0.01), a thermometer (± 0.02), a measuring cylinder (± 0.03) and a beaker (± 0.04) during an experiment. Which of the above instrument is more precise?

• The beaker

• The digital balance

• The thermometer

• The measuring cylinders

Which of the following postulates of Dalton’s atomic theory is disproved by the modern atomic theory?

• Atoms combine in small whole numbers to form compounds

• Elements are made up of small particles called atoms

• Atoms of different elements have different masses and size

• All atoms of the same elements are identical and have the same mass

The main purpose of Robert Millikan’s oil drop experiment is to determine

• the ratio of mass of electron to charge of electron

• the speed of electron

• the magnitude of charge of electron

• the mass of electron

Pb has an average atomic mass of 207.19 amu. The three major isotopes of Pb-206 (205.98 amu), Pb-207 (206.98 amu) and Pb-208 (207.98 amu). If the isotopes of Pb-207 and Pb-208 are present in equal amounts, what is the percent abundance of Pb-206, Pb-207 and Pb-208 respectively?

• 19.34 %, 40.33 % and 40.33 %

• 24.16 %, 37.92 % and 37.92 %

• 15.22 %, 42.39 % and 42.39 %

• 34.08 %, 32.96 % and 32.96 %

Which region of electromagnetic spectrum is capable of inducing electron transition with the greatest energy?

• Orange

• Red

• Violet

• Green

What is the wavelength of the yellow sodium emission, which has a frequency of 5. 09 x 10 14 s-1? (C = 3 x 10 8 m/s)

• 400nm

• 589nm

• 670nm

• 890nm