EmSAT EmSAT Chemistry 1

Question 1

What is the electron configuration of oxygen (atomic number 8)?

Accepted Answer

1s² 2s² 2p⁴

Answer

Oxygen has 8 electrons. The configuration is 1s² 2s² 2p⁴ — 2 in the first shell and 6 in the second shell (2 in 2s and 4 in 2p).

Question 2

What type of bond is formed between Na and Cl in NaCl?

Accepted Answer

Ionic bond

Answer

NaCl forms an ionic bond. Sodium (a metal) transfers an electron to chlorine (a non-metal), creating Na⁺ and Cl⁻ ions that attract each other electrostatically.

Question 3

What is Avogadro's number?

Accepted Answer

6.022 × 10²³

Answer

Avogadro's number is 6.022 × 10²³, representing the number of particles (atoms, molecules, ions) in one mole of a substance.

Question 4

Balance the equation: H₂ + O₂ → H₂O

Accepted Answer

2H₂ + O₂ → 2H₂O

Answer

Balanced: 2H₂ + O₂ → 2H₂O. Left: 4H, 2O. Right: 4H, 2O. Both sides are equal, satisfying conservation of mass.

Question 5

What is the pH of a neutral solution at 25°C?

Accepted Answer

7

Answer

A neutral solution at 25°C has pH = 7. pH < 7 is acidic, pH > 7 is basic (alkaline). Pure water at 25°C is neutral with pH = 7.

EmSAT Practice Test

EmSAT Practice Test

EmSAT EmSAT Chemistry 1