2g of brass containing Cu and Zn only reacts with 3M HNO3 solution- Following are the reactions taking place- Cus-HNO3aq- Cu2-aq-NO2g-H2Ol Zns-H-aq-NO-3aq- NH-4aq-Zn2-aq-H2OlThe liberated NO2g was found to be 1-04L at 25o and 1 atm -Cu -63-5- Zn-65-4-The percentage by mass of Cu in brass was-

The correct option is A 67% Let, wt. of Cu in brass =W g_m . #160; First reaction (Balanced) : [ Cu(s)+4 HNO_3⟶ 2NO_2+2 H_2O+Cu(NO_3)_2; ...

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Byju's Answer

Standard XII

Chemistry

Sulphur Dioxide

2g of brass c...

Question

$2$ g of brass containing Cu and Zn only reacts with $3$ M $H N O_{3}$ solution. Following are the reactions taking place:

$C u (s) + H N O_{3} (a q) \to C u^{2 +} (a q) + N O_{2} (g) + H_{2} O (l)$

$Z n (s) + H^{+} (a q) + N O_{3}^{-} (a q) \to N H_{4}^{+} (a q) + Z n^{2 +} (a q) + H_{2} O (l)$

The liberated $N O_{2} (g)$ was found to be $1.04$ L at $25^{o}$ and $1$ atm $[C u = 63.5, Z n = 65.4]$ .
The percentage by mass of Cu in brass was?

67 %

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70 %

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80 %

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90 %

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Solution

The correct option is A $67 %$
$Let, wt. of C u in brass = W g_{m} .$

$\frac{First reaction}{(Balanced)} : \begin{matrix} C u (s) + 4 {H N O}_{3} ⟶ 2 {N O}_{2} + 2 H_{2} O + C u {({N O}_{3})}_{2} t = 0 \frac{W}{63.5} \end{matrix}$

$\begin{matrix} Here, 1 m o l of C u can produce 2 m o l e s {N O}_{2} . Thus, 2 \times \frac{W}{63.5} = \frac{P_{{N O}_{2}} V_{{N O}_{2}}}{R T} = \frac{1 \times 1.04}{0.0821 \times 298} \end{matrix}$

$∴ W = 1.35 g m$

$\begin{matrix} So, weight of C u = 1.35 g m and weight of Z n = 0.65 g m . Thus, % - by mass of C u = \frac{1.35}{2} \times 100 = 67.5 % \end{matrix}$

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Similar questions

1.5

g of brass containing

C u

and

Z n

reacts with

3.0 M

H N O_{3}

solution. The following reactions take place:

C u + H N O_{3} \to C u^{2 +} + N O_{2} (g) + H_{2} O

Z n + H^{⨁} + N O_{3}^{⊝} \to N H_{4}^{⨁} + Z n^{2 +} + H_{2} O

The liberated

N O_{2} (g)

was found to be

1.04

L at

25^{o} C

and

1

atm.
a. Calculate the percentage composition of brass.
b. How many mL of

3.0 M

H N O_{3}

will be required for complete reaction with

1.0

g of brass?

C u + H N O_{3} ⟶ C u^{2 +} + N O_{2} (g) + H_{2} O

Z n + H^{+} + N O_{3}^{-} ⟶ N H_{4}^{+} + Z n^{2 +} + H_{2} O

The above reaction takes place when

1.5

g of brass containing

C u

and

Z n

reacts with

3 M H N O_{3}

solution. The liberated

N O_{2}

(g) was found to be

1.04

litres at

25^{\circ} C

and one atm pressure. Calculate the

%

composition of brass.

C u + H N O_{3} ⟶ C u^{2 +} + N O_{2} (g) + H_{2} O

Z n + H^{+} + N O_{3}^{-} ⟶ N H_{4}^{+} + Z n^{2 +} + H_{2} O

The above reaction takes place when

1.5

g of brass containing

C u

and

Z n

reacts with

3 M H N O_{3}

solution. The liberated

N O_{2}

(g) was found to be

1.04

litres at

25^{\circ} C

and one atm pressure. How many mL of

3 M

H N O_{3}

will be required for completely reacting

1

g of brass?

Q. For

C u (s) + N O_{3}^{-} (a q) + H^{+} (a q) \to C u^{2 +} (a q) + N O_{2} (g) + H_{2} O (l)

, which of the following takes place?

Q. Calculate

E_{C e l l}^{o}

value of the following reactions:

Z n (s) + C u^{2 +} (a q) \to Z n^{2 +} (a q) + C u (s)

[Given:

E_{C u^{2 +} / C u}^{\circ} = 0.34 V, E_{Z n^{2 +} / Z n}^{\circ} = - 0.76 V

]

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