1
IIT-JEE 1979
Subjective
+2
-0
The precipitation of second group sulphides in qualitative analysis is carried out with hydrogen sulphide in the presence of hydrochloric acid but not in nitric acid. Explain.
2
IIT-JEE 1979
+2
-0.5
If $$\tan \theta = - {4 \over 3},then\sin \theta \,is\,$$
A
$$- {4 \over 5}\,but\,not\,{4 \over 5}$$
B
$$- {4 \over 5}\,or\,{4 \over 5}$$
C
$${4 \over 5}\,\,but\,not\, - {4 \over 5}$$
D
None of these.
3
IIT-JEE 1979
+2
-0.5
If $$\alpha + \beta + \gamma = 2\pi ,$$ then
A
$$tan{\alpha \over 2} + \tan {\beta \over 2} + \tan {\gamma \over 2} = \tan {\alpha \over 2}\tan {\beta \over 2}\tan {\gamma \over 2}$$
B
$$\tan {\alpha \over 2}\tan {\beta \over 2} + \tan {\beta \over 2}\tan {\gamma \over 2} + \tan {\gamma \over 2}\tan {\alpha \over 2} = 1$$
C
$$tan{\alpha \over 2} + \tan {\beta \over 2} + \tan {\gamma \over 2} = - \tan {\alpha \over 2}\tan {\beta \over 2}\tan {\gamma \over 2}$$
D
None of these.
4
IIT-JEE 1979
+2
-0.5
If the cube roots of unity are $$1,\,\omega ,\,{\omega ^2},$$ then the roots of the equation $${\left( {x - 1} \right)^3} + 8 = 0$$ are
A
$$- 1,1 + 2\omega ,\,1 + 2{\omega ^2}$$
B
$$- 1,1 - 2\omega ,\,1 - 2{\omega ^2}$$
C
$$- 1, - 1, - 1$$
D
None of these
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