Chemistry
Which of the following is used in welding broken pieces of iron rails and machine parts?

Solder
Aluminium powder
Aluminium sulphate
None of these

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Chemistry
Photo chemical smog is a resultant of the reaction among

CO, O2 and peroxy acetyl nitrate in the presence of Sunlight
CO, CO2 and NO2at low temperature
High concentration of NO2, O3, and CO in the evening
NO2, O3 and peroxy acetyl nitrate in the presence of Sunlight

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