9. the molar mass of na2so4 is 142.1 g/mol.
calculate the number of moles in 10.0 g of na2so4.

• 7 x 6.02 x 10^23 x 142.1 g/mol
• 10.0 g/ 142.1 g/mol
• 7 x 10.0g/142.1 g/mol
• 10.0g x 142.1 g/mol

the Answer is the second one

Explanation:

mole=mass/molar mass

mole=?

molar mass=142.1g/mole

mass=10.0g

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

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.