Answer:

Explanation:
Given :
Mass of a bar of lead = 115.2 g
Initial water level
= 25 mL
Final water level
= 35.5 mL
Difference in the water level = 35.5 - 25
= 10.5 mL
= 
We know that when a body is submerged in water, it displaces its own volume of water.
Therefore, the volume of the lead bar = volume of the water displaced = 10.5 mL = 
We know that mathematically, density is the ratio of mass of body to its volume.
Density of the lead bar is given by :


= 
Li2O is the formula for <span> lithium oxide</span>
Answer:
5.79 × 10^23 Oxygen atoms
Explanation:
Number of Oxygen atom in the compound = 4×3 = 12
Molar mass of Al2(SO4)3 = 342 g/mol.
No of mole = mass/molar mass = 2.74/342 = 8.01×10^-03 mole
2.74g of Al2(SO4)3 × 1 mole of Al2 (SO4)3 / 342g of Al2 (SO4)3 * 12 mole of Oxygen/ 1mole of Al(SO4)3 * 6.02×10^23 Oxygen atom/ 1 mole of Oxygen
= 5.79×10^23 Oxygen atoms