asbestos dust
sawdust
nitrogen (II) oxide
carbon (II) oxide
Correct answer is A
No explanation has been provided for this answer.
Pollution of underground water by metal ions is very likely in the soil that has high
acidity
alkalinity
chloride content
nitrate content
Correct answer is D
Trioxonitrate(v) salts are generally d only soluble salts of some metals.All trioxonitrate(v) salts r soluble in water. Therefore d metal ions found in underground water, are derived mostly 4rm d soluble nitrates (Trioxonitrate(v) salts) of those metals.
Hardness of water is caused by the presence of ions of
magnesium and silver
cacium and magnesium
sodium and potassium
calcium and sodium
Correct answer is B
No explanation has been provided for this answer.
Which of the following mixture of gases is likely to burn in flame
neon and hydrogen
nitrogen and helium
helium and neon
neon and nitrogen
Correct answer is A
No explanation has been provided for this answer.
20
25
60
75
Correct answer is B
Let the relative abundance of oxygen with mass 37 be x%
∴ The relative abundance of the isotope of mass 35 = (100 - x)%. Total mass of isotopes of mass 37 = 37x, while that of 35 = 35(100 - x)
∴ Total mass of the 100 atoms
= 37x + 35(100 - x) = 35.5
= 37x + 3500 - 35x = 35.5
∴ Mean mass of chlorine atom = (2x + 3500)/100 = 35.5
2x + 3500 = 3550; x = 50/2 = 25