220g of carbon dioxide contains ----- moles
5
6
3
4
Correct answer is A
One mole of carbon dioxide molecules has a mass of 44.01 g,
: 5 mole of carbon dioxide molecules has a mass of 220g
The mass of one Avogadro number of helium atoms is?
1.00gram
4.00gram
8.00gram
6.00gram
Correct answer is B
Avogadro's number is an absolute number: there are 6.022×10\(^23\) elementary entities in 1 mole.
helium has a molar mass of 4.0 grams per mole. So one mole of helium has a mass of 4.0 grams.
The mass number of a nucleus is?
Always less than its atomic number
The sum of the number of protons and neutrons present in the nucleus
Always more than the atomic weight
A fraction
Correct answer is B
mass number, is the sum of the numbers of protons and neutrons present in the nucleus of an atom.
The reactivity of fluorine is due to?
its high electro negativity
small size of fluorine atom
availability of D-orbitals
strong f-f bond
Correct answer is A
fluorine (F), most reactive chemical element and the lightest member of the halogen elements.
As the most electronegative element, it is extremely reactive.
Soaps clean surfaces on the principle based on?
viscosity
floatation
elasticity
surface tension
Correct answer is D
Since the surface tension forces become smaller as the distance between water molecules increases, the intervening soap molecules decrease the surface tension.