Question

please help asap!!
1. what is the mass (in amu) of 5 potassium atoms?
2. how many atoms are present in a sample of 630.4 amu of manganese?
3. which contains more atoms: one mole of copper or one mole of gold? explain your answer.
4. given a sample of 12g if aluminum, how many moles do you have?
5. how many atoms are in 2 moles of lithium?
6. what is the mass (in grams) of 3.13 x 10^21 atoms of potassium?

Answer 1

Explanation:

1) mass of 1 K atom is 39 amu

5k atoma have 5×39=195amu

2) mass of 1 atom of manganese is 54.94amu

mass of x atoms is 630.4 amu

no of atms=630.4÷54.94=11.47 atoms

3)molar mass of aluminium is 27 g/mol

mass =12g

no of moles=mass/molarnass=12/27=0.44moles

5)no of moles=no of atoms/avogadro number

=2=no of atoms /6.02×10^23

no of atoms =2×6.02×10^23=12.04×10^23atoms

6)no of moles=no of atoms/6.02×10^23

=3.13×10^21/6.02×10^23=0.519×10^-2moles

0.519×10^-2=mass/39

mass=39×0.519×10^-2=20.241×10^-2grams