The presence of an impurity in substance will cause the melting point to

A. be zero

B. reduce

C. increase

D. be stable

What volume of carbon (ll) oxide is produced by reacting excess carbon with 10 dm³ of oxygen?

A. 5 dm ³

B. 20 dm ³

C. 15 dm ³

D. 10 dm ³

The radioisotope used in industrial radiography for the rapid checking of faults in welds and casting is

A. carbon-14

B. phosphorus-32

C. cobalt-60

D. iodine-131

The shape of the carbon (lV) oxide molecule is

A. pyramidal

B. linear

C. angular

D. tetrahedral

Which of the following molecules is held together by hydrogen bond?

A. CH₄

B. HBr

C. H₂SO₄

D. HF

The bond formed between two elements with electron configurations 1s² 2s² 2p⁶ 3s² and 1s² 2s² 2p⁴ is

A. metallic

B. covalent

C. dative

D. ionic

The constituent of air that acts as a diluent is

A. nitrogen

B. carbon (IV) oxide

C. noble gases

D. oxygen

Steam changes the colour of anhydrous cobalt (ll) chloride from

A. white to red

B. blue to white

C. blue to pink

D. white to blue

An example of a hygroscopic substance is

A. CuO _(S).

B. MgCL_2(S).

C. CaCL_2(S).

D. NaOH_(S).