WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995

1989 WAEC Chemistry Theory (a) Explain the differences in the reactions of zinc with dilute trioxonitrate (V) acid and...

Chemistry
WAEC 1989

(a) Explain the differences in the reactions of zinc with dilute trioxonitrate (V) acid and zinc with dilute hydrochloric acid.

(b) Write equations to illustrate how ammonia gas can be converted into trioxonitrate (V) acid.

(c) Calculate the mass of sodium trioxonitrate (V) produced when 30.0g of pure sodium hydroxide reacts with 100cm\(^3\) of 1.00 M trioxonitrate (V) acid. (H =1, N = 14, 0 = 16, Na = 23)

(d) Write the equations for the decomposition by heat of:

(i) sodium trioxonitrate(V);

(ii) copper (II) trioxonitrate (V);

(iii) mercury (II) trioxonitrate (V);

WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Explanation

(a) Zinc reacts with dilute hydrochloric acid to produce hydrogen as but with trioxonitrate (VI) acid. the hydrogen initially produced is at once oxidized by the powerful oxidizing ability of the trioxonitrate (V) acid to give water and the reduction products of the acid.

(b) Step I 4NH\(_{3(g)}\) + SO\(_{2(g)}\) --> 4NO\(_{(g)}\) + 6H\(_2\)O\(_{(l)}\)

Step II 2NO\(_{(g)}\) + O\(_{2(g)}\) —> 2NO\(_{2(g)}\)

Step III 2H\(_2\)O\(_{(l)}\) + 4NO\(_{2(g)}\) + O\(_{2(g)}\) —> 4HNO\(_{3(aq)}\)

 

(c) NaOH(\(_{(aq)}\) + HNO\(_{3(aq)}\) —> NaNO\(_{3(aq)}\) + H\(_2\)O\(_{(l)}\)

30g NaOH x \(\frac{1 mole}{g}\)

Since mole = concentration x volume

Mole HNO\(_3\) = 1.00 mole x 100dm\(^3\) = 0.1 mole dm\(^3\)

From the balanced neutralization reaction, 

\(\frac{NaOH}{HNO_ 3}\) = \(\frac{1}{1}\)

 i.e mole NaOH = mole HNO\(_3\). The limiting reagent in the above rxn, is 0.1 mole HNO\(_3\)

0.1 mole HNO\(_3\) will produce 85 x 0.1 = 8.5g NaNO\(_3\)

 

(d)(i) 2NaNO\(_{3(g)}\) \(\to\) 2NaNO\(_{2(g)}\) + O\(_{2(g)}\)

(ii) 2Cu(NO\(_3\))\(_{2(g)}\) \(\to\) 2CuO\(_{(g)}\) + 4NO\(_2\) + O\(_{2(g)}\)

(iii) Hg(NO\(_3\))\(_{2(g)}\) -> Hg\(_{(l)}\) + 2NO\(_{2(g)}\) + O\(_{2(g)}\)

 


Report an Error Ask A Question Download App
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709

Contributions ({{ comment_count }})

Please wait...

{{ settings.no_comment_msg ? settings.no_comment_msg : 'There are no comments' }}

Quick Questions

Post your Contribution

Please don't post or ask to join a "Group" or "Whatsapp Group" as a comment. It will be deleted. To join or start a group, please click here

{{ quote.posted_by.display_name }}
{{ settings.form_textarea_description }}
 
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC offline past questions - with all answers and explanations in one app - Download for free