Problem 34
The presence of fluoride ion in polluted water can be detected by using (a) KI+ starch (b) zirconium alizarin-S dye (c) \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+50 \% \mathrm{H}_{2} \mathrm{SO}_{4}\) (d) sodium nitroprusside
Problem 35
The phosphates present in sewage water which cause eutrophication can be removed by adding (a) alum (b) chlorine (c) lime (d) permanganate
Problem 36
Ozone is an important constituent of stratosphere because it (a) removes poisonous gases of the atmosphere by reacting with them (b) destroys bacteria which are harmful to human life (c) prevents the formation of smog over large cities (d) absorbs ultraviolet radiation which is harmful to human life
Problem 38
The excessive use of phosphates as water softeners leads to aquatic pollution called (a) eutrophication (b) phosphorylation (c) deoxygenation (d) denitrification
Problem 39
Spraying of DDT causes pollution of (a) air (b) air and water (c) air and soil (d) air, water and soil
Problem 40
Which of the following causes water pollution? (a) fly ash (b) pesticides (c) auto exhausts (d) aeroplanes
Problem 41
Ozone layer is present in (a) stratosphere (b) troposphere (c) mesosphere (d) exosphere
Problem 42
Human ear can tolerate noise upto (a) 100 decible (b) 80 decible (c) 60 decible (d) 40 decible
Problem 43
Sound pollution is mainly due to (a) industrial estates (b) airport, railway stations (c) sound systems (d) all of these
Problem 44
Ozone hole is maximum over (a) Africa (b) Europe (c) Antarctica (d) India
