They have high melting and boiling points and are hard and brittle
Answer:
The difference in mass between 3.01×10^24 atoms of gold and a gold bar with the dimensions 6.00 cm X 4.25 cm X 2.00 cm is :
<u>Difference</u> <u>in mass</u> =<u> 985.32 - 984.5 = 0.82 g</u>
Explanation:
<u>Part I :</u>

n = 4.9983
n = 4.99 moles
(Note : You can also take n = 5 mole )
Molar mass of gold = 196.96 g/mole
This means, 1 mole of gold(Au) contain = 196.96 grams
So, 4.99 moles of gold contain =
g
4.99 moles of gold contain = 984.8 g
Mass of
atoms of gold = 984.5 g
<u>Part II :</u>
Density of Gold = 
Volume of the cuboid = 
Volume of the gold bar =
Volume of the gold bar = 51
Using formula,

Mass = 985.32 g
So, A gold bar with the dimensions 6.00 cm X 4.25 cm X 2.00 cm has mass of <u>985.32 g</u>
<u>Difference</u> <u>in mass</u> =<u> 985.32 - 984.5 = 0.82 g</u>
Answer: Mass of
produced in this reaction was 6.56 grams
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

Mass or reactants = Mass of
+ mass of
= 16.00 + 64.80 = 80.80 g
Mass of products = mass of aqueous solution + mass of
+ = 74.24 + x g
Mass or reactants = Mass of products
80.80 g = 74.24 + x g
x = 6.56 g
Thus mass of
produced in this reaction was 6.56 grams
Considering ideal gas:
PV= RTn
T= 25.2°C = 298.2 K
P1= 637 torr = 0.8382 atm
V1= 536 mL = 0.536 L
:. R=0.082 atm.L/K.mol
:. n= (P1V1)/(RT) = ((0.8382 atm) x (0.536 L))/
((0.082 atmL/Kmol) x (298.2K))
:. n= O.0184 mol
Then,
P2= 712 torr = 0.936842 atm
V2 = RTn/P2 = [(0.082atmL/
Kmol) x (298.2K) x (0.0184mol) ]/(0.936842atm)
:.V2 = 0.4796 L
OR
V2 = 479.6 ml
C is the answer hope the answer is right