An aluminum sample has a mass of 80.01 g and a density of 2.70 g/cm3. according to the data, to what number of significant figures should the calculated volume of the aluminum sample be expressed?

Answer : The volume of aluminium sample should be

Explanation :

Density : It is defined as the mass contained per unit volume.

Formula used :

Given :

Mass of aluminum = 80.01 g

Density of aluminium =

Now put all the given values in the above formula, we get :

Therefore, the volume of aluminium sample should be

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.