Revision 30s

Which atom has the smallest number of neutrons?

• Carbon-14
• Neon-20

• Fluorine-19
• Nitrogen-14

The oxygen element consist of three naturally occurring isotopes : ¹⁶O, O¹⁷ and O¹⁸. The atomic mass of oxygen is 16.0 u. What can be implied about the relative abundances of these isotopes?

• Almost all O atoms are O¹⁸
• The isotopes all have the same abundance
• The abundances of O¹⁷ and O¹⁸ are very small
• ¹⁶O have lowest abundance

The mass of bromine atom is about four times greater than that of neon atom. What is the relative numbers of bromine and neon atoms in 1000 g of

• 1 : 4
• 4 : 1
• 1 : 1000
• 1000 : 1

Which of the following solutions with a concentration of 0.100 M contain the highest concentration of potassium ions?

• potassium iodide
• Ni
• potassium hypochlorite
• potassium phosphate

How many nitrogen atoms are present in 28 L of nitrogen gas at STP?(Molar volume of gas = 22.4 L at STP ; Avogadro constant = 6.02 x 10²³)

• 1.5 x 10²³ atoms
• 7.5 x 10²³ atoms
• 1.5 x 10²⁴ atoms
• 3.0 x 10²⁴ atoms

Which of the following equations does not represent a redox equation?

• 2H₂O ⎯→ 2H₂ + O₂
• Cu(NO₃)₂ + Zn ⎯→ Zn(NO₃)₂ + Cu
• 2NaI + Br₂⎯→ 2NaBr + I₂
• 2NaCl + Pb(NO₃)₂⎯→ PbCl₂ + 3NaNO₃

In the reaction, Zn + 2HCl→ ZnCl₂ + H₂, 25.0 grams of Zn are reacted with 17.5 g of HCl. How many grams of H₂ will be produced?

• 0.479 g
• 0.382 g
• 0.765 g
• 0.250 g

An experiment was carried out and the product obtained was 122 grams. If the theoretical yield for the reaction was 156 grams, what is percentage yield of the product?

• 78.2%
• 72.8%
• 19.0%
• 18.6%

Calculate the wavelength, λ, for the fourth line in Balmer series.

• 410.0 nm

• 432.0 nm
• 486.0 nm
• 654.0 nm

Choose the highest energy involved when an electron makes a transition.

• n₃ to n₁
• n₂ to n₁
• n₄ to n₂
• n₄ to n₃