Nitrogen and phosphorus are elements in Group 15 of the Periodic Table. A common test for nitrates is the reaction with NaOH and Al . Equation 1 shows the reaction. (i) Deduce the oxidation state of nitrogen in $$$\mathrm{NO}_{3}{ }^{-}$$$. ................................................................................................................................. (ii) Identify the species that is oxidised in equation 1. ................................................................................................................................. . (iii) $$$\mathrm{NH}_{3}$$$ is a basic gas. Describe how $$$\mathrm{NH}_{3}$$$ is able to act as a base. ....................................................................................................................................... . ................................................................................................................................. (iv) Suggest the shape of the $$$\left[\mathrm{Al}(\mathrm{OH})_{4}\right]^{-}$$$ion. .................................................................................................................................

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_w24_qp_22 Year：2024 Question No：3(b)

Answer:

Knowledge points:

6.1.1 calculate oxidation numbers of elements in compounds and ions

6.1.2 use changes in oxidation numbers to help balance chemical equations

6.1.3 explain and use the terms redox, oxidation, reduction and disproportionation in terms of electron transfer and changes in oxidation number

6.1.4 explain and use the terms oxidising agent and reducing agent

6.1.5 use a Roman numeral to indicate the magnitude of the oxidation number of an element

7.2.1 state the names and formulae of the common acids, limited to hydrochloric acid, HC/, sulfuric acid, ethanoic acid,

7.2.10 select suitable indicators for acid-alkali titrations, given appropriate data

7.2.2 state the names and formulae of the common alkalis, limited to sodium hydroxide, NaOH, potassium hydroxide, KOH, ammonia,

7.2.3 describe the Brønsted–Lowry theory of acids and bases

7.2.4 describe strong acids and strong bases as fully dissociated in aqueous solution and weak acids and weak bases as partially dissociated in aqueous solution

7.2.5 appreciate that water has pH of 7, acid solutions pH of below 7 and alkaline solutions pH of above 7

7.2.6 explain qualitatively the differences in behaviour between strong and weak acids including the reaction with a reactive metal and difference in pH values by use of a pH meter, universal indicator or conductivity

7.2.7 understand that neutralisation reactions occur when

7.2.8 understand that salts are formed in neutralisation reactions

7.2.9 sketch the pH titration curves of titrations using combinations of strong and weak acids with strong and weak alkalis

Answer:

Knowledge points:

Solution:

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