Hóa 8

Humans can quantify natural objects and phenomena based on which skill?

• Skill of observation and classification

• Skill of linking knowledge

• Skill of prediction

• Skill of measurement

When conducting an experiment, what should be done when cleaning up a broken mercury thermometer?

• Close the door, wear a mask and gloves, use a soft brush to clean up

• Open the window, let the mercury evaporate outside, wear gloves and a mask when cleaning up

• Quickly sweep up with a broom and dustpan, no need to wear a mask

• Close the door and go outside

The total number of protons, neutrons, and electrons in 2 atoms A and B is 177, with the total number of charged particles exceeding the uncharged particles by 47. The number of charged particles in atom B exceeds that of A by 8. A, B are respectively

• Fe, Zn

• Fe, Cu

• Na, Mg

• Ca, Fe

The number of atoms in 1 mole of molecule X is 24.08 x 10^23. X could be which of the following substances?

• CuCl2

• HNO3

• H2O

• SO3

In the molecule KCl, potassium and chlorine atoms are bonded together by which type of bond?

• Covalent bond

• Ion

• Metallic

• Non-metallic

The chemical bond between oxygen and hydrogen atoms is formed by

• Oxygen atom accepts electrons, hydrogen atom donates electrons

• Oxygen atom donates electrons, hydrogen atom accepts electrons

• Oxygen and hydrogen atoms share electrons

• Oxygen and hydrogen atoms share protons

In the reaction: Fe + KMnO4 + KHSO4 -> Fe2(SO4)3 + K2SO4 + MnSO4 + H2O, the minimal whole number coefficients of Fe and KHSO4 after balancing the chemical equation are

• 38

• 48

• 58

What is the total smallest integer coefficient of Fe and KHSO4 in the chemical equation after balancing?

• 38

• 48

• 58

• 42

Which experiment among the following involves a chemical change?

What is the efficiency of the reaction when 5 tons of calcium carbonate produces 2.45 tons of calcium oxide?

• 87.5%

• 88%

• 91%

• 87%