Correct Answer: (D) come/has

Correct Answer: B. Igbo, by consensus

Correct Answer: B. number of feet it contains

Correct Answer: D. though

Correct Answer: A. Na₂O₂

Explanation

A peroxide is a chemical compound that contains an oxygen-oxygen single bond (-O-O-) and has the peroxide ion (O₂²⁻), where each oxygen atom has an oxidation state of -1.

Let's analyze each option:

• A. Na₂O₂ (Sodium peroxide)

* Sodium (Na) typically forms a +1 ion (Na⁺).

* Since there are two Na⁺ ions, the charge of the oxygen part must be -2.

* Thus, the oxygen exists as O₂²⁻. This is the peroxide ion.

* Therefore, Na₂O₂ is a peroxide.

• B. CuO (Copper(II) oxide)

* Copper in this compound is typically in the +2 oxidation state (Cu²⁺).

* The oxygen is in the -2 oxidation state (O²⁻).

* This is a simple metal oxide, not a peroxide.

• C. PbO₄

* This formula is not for a common or stable simple oxide or peroxide of lead. Common lead oxides include PbO, PbO₂, and Pb₃O₄.

* If lead were +4 (Pb⁴⁺), the oxygen would have to have an average oxidation state of -1 (O₄⁴⁻), which doesn't correspond to a simple peroxide. If it were a peroxide with Pb²⁺, the formula would be PbO₂, containing Pb²⁺ and O₂²⁻, but PbO₂ is more commonly known as lead dioxide where Pb is +4 and O is -2.

* Therefore, PbO₄ is not identifiable as a simple peroxide.

• D. Fe₂O

* This is not a common or stable oxide of iron. Common iron oxides are FeO, Fe₂O₃, and Fe₃O₄.

* Even if it existed, it would not contain the O₂²⁻ peroxide ion.

Based on the definitions, Na₂O₂ is clearly a peroxide because it contains the O₂²⁻ ion.

The final answer is A

Correct Answer: D. She stoops to Conquer

Correct Answer: C. tractor

Correct Answer: D. Temperature

Explanation

(a)(i) E = W + K.E, where

E = energy of incident radiation

W = work function of metal

K.E. = Kinetic energy of ejected electrons

(ii) The equation represents the principle of conservation of energy.

(b) Applications of photocells:

1. for burglar alarm

2. for television cameras

3. automatic doors

4. automatic street lighting

5. automatic digital counters.

(c)(i) V = \(f_o\lambda_o\)

\(\lambda_o = \frac{v}{f_o} = \frac{3 \times10^8}{4.02 \times 10^{14}}\)

= 7.46 x 10\(^{-7}\)m

(ii) W = \(hf_o = 6.63 \times 10^{-34} \times 4.02 \times 10^{14}\)

= 2.67 x 10\(^{-19}\)J

(iii) K.E. = \(h (f - f_o) = 6.63 \times10^{-34} (5.0 \times 10^{15} - 4.02 \times 10^{14})\)

= 3.05 x 10\(^{-15}\)J

Correct Answer: C. Microtubules

Explanation

Microtubules are hollow tubes made up of polymerized tubulin that provide support throughout the cell.