EIT Chemistry and Materials Science

Question 1

The atomic number of an element represents the number of:

Accepted Answer

Protons in the nucleus

Answer

The atomic number Z uniquely identifies an element and equals the number of protons in the nucleus.

Question 2

Avogadro's number (6.022 × 10²³) represents the number of entities in:

Accepted Answer

One mole of a substance

Answer

One mole of any substance contains exactly 6.022 × 10²³ particles (atoms, molecules, ions, etc.).

Question 3

The pH of a neutral aqueous solution at 25°C is:

Accepted Answer

7

Answer

At 25°C, pure water has [H⁺] = [OH⁻] = 10⁻⁷ mol/L, giving pH = −log(10⁻⁷) = 7.

Question 4

The ideal gas law PV = nRT uses R = 8.314 J/(mol·K) when pressure is in:

Accepted Answer

Pascals (Pa)

Answer

R = 8.314 J/(mol·K) = 8.314 Pa·m³/(mol·K), consistent with SI units where P is in Pascals and V in m³.

Question 5

The crystal structure of iron (Fe) at room temperature is:

Accepted Answer

Body-centered cubic (BCC)

Answer

Iron is BCC at room temperature (α-iron), transforming to FCC (γ-iron) above 912°C.

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