Q1.What is the mass of 5 moles Of 1.Mg 2.CaCO3 Q2. Calculate the number of atoms in 10g of Na Q3.calculate the number of molecules in 10g of NaCl Q.4.What is Avogadro's number? How many number of atoms are present in 4g of Oxygen?

Explanation:

Q1) as we know that moles=given mass/molar mass

     mass of 5 moles of Mg is

mass =moles*molar mass

mass=5*24

mass=120 g

mass of 5 moles of CaCO3 is

mass= moles*molar mass

mass=5*100=500

Q2) number of atoms in 10 g Na

first we need number of moles of sodium

moles =mass/molar mass

moles=10/23=0.43

now we know that moles=number of atoms /avogadro number

for number of atom the formula become

number of atom=moles*avogadro number

number of atom=0.43*6.023*10^23=2.6*10^23

Q3)number of molecule in 10 g of NaCl

again we need number of moles of NaCl

moles=given mass/molar mass

moles=10/58.5=0.17

now number of molecules=moles*avogadro number

number of molecules=0.17*6.023*10^23=1.02*10^23

Q4) avogadro number is the number of particles(atoms,molecules,ions) present in one mole of a substance its value is 6.023*10^23

Q5)Number of atoms in 4g of oxygen

again we need number of moles of oxygen

moles=mass/molar mass

moles=4/16=0.25

now number of atoms=moles*avogadro number

number of atoms=0.25*6.023*10^23 =1.5*10^23

the answer is 75.0%.