4.2 Covalent Bonding - EWEWEWEWE PDF

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4.2 Covalent Bonding 1. [1 mark] Which compound has the shortest C–N bond? A. CH3NH2 B. (CH3)3CNH2 C. CH3CN D. CH3CHNH 2. [1 mark] The electronegativity values of four elements are given.

What is the order of increasing polarity of the bonds in the following compounds? A. CO < OF2 < NO < CF4 B. CF4 < CO < OF2 < NO C. NO < OF2 < CO < CF4 D. CF4 < NO < OF2 < CO 3. [1 mark] Which two atoms form the most polar bond? A. C and F B. C and Cl C. Si and F D. Si and Cl 4. [1 mark] Which bonds cause the boiling point of water to be significantly greater than that of hydrogen sulfide? 1

A. London (dispersion) B. Covalent C. Ionic D. Hydrogen 5. [1 mark] How many bonding electrons are there in the urea molecule?

A. 8 B. 16 C. 20 D. 24 6. [1 mark] Which compound contains both ionic and covalent bonds? A. SIH4 B. NaNO3 C. H2CO D. Na2S 7. [1 mark] Which molecule is non-polar? A. OF2 B. NH3 C. BF3 2

D. SO2 8. [1 mark] How many electrons form the carbon–oxygen bond in methanal, HCHO? A. 2 B. 4 C. 8 D. 12 9a. [2 marks] Bonds can be formed in many ways. The landing module for the Apollo mission used rocket fuel made from a mixture of hydrazine, N 2H4, and dinitrogen tetraoxide, N2O4. N2H4(l) + N2O4(l) → 3N2(g) + 4H2O(g) State and explain the difference in bond strength between the nitrogen atoms in a hydrazine and nitrogen molecule.

9b. [1 mark] State why hydrazine has a higher boiling point than dinitrogen tetraoxide.

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9c. [2 marks] Deduce the Lewis (electron dot) structures of ozone.

10a. [8 marks] Phosphine (IUPAC name phosphane) is a hydride of phosphorus, with the formula PH 3. (i) Draw a Lewis (electron dot) structure of phosphine. (ii) Outline whether you expect the bonds in phosphine to be polar or non-polar, giving a brief reason. (iii) Phosphine has a much greater molar mass than ammonia. Explain why phosphine has a significantly lower boiling point than ammonia.

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10b. [8 marks] Phosphine is usually prepared by heating white phosphorus, one of the allotropes of phosphorus, with concentrated aqueous sodium hydroxide. The equation for the reaction is:

(i) The first reagent is written as P4, not 4P. Describe the difference between P 4 and 4P.

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10c. [4 marks] 2.478 g of white phosphorus was used to make phosphine according to the equation:

(i) Calculate the amount, in mol, of white phosphorus used. (ii) This phosphorus was reacted with 100.0 cm 3 of 5.00 mol dm−3 aqueous sodium hydroxide. Deduce, showing your working, which was the limiting reagent. (iii) Determine the excess amount, in mol, of the other reagent. (iv) Determine the volume of phosphine, measured in cm3 at standard temperature and pressure, that was produced.

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11a. [1 mark] Materials science involves understanding the properties of materials and applying those properties to desired structures. Magnesium oxide, MgO, and silicon carbide, SiC, are examples of ceramic materials. State the name of the predominant type of bonding in each material.

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11b. [1 mark] Predict the predominant type of bonding for a binary compound AB in which the electronegativity of both atoms is low. Use section 29 of the data booklet.

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