49)Solid sodium metal reacts violently with water, producing hydrogen gas (H2) and sodium hydroxide. How many moles of hydrogen gas are formed when 15.3 g of sodium are added to water?

Number of moles of hydrogen gas produced when 15.3 g of sodium reacts with water = 0.333 moles of hydrogen gas

Explanation:

The reaction between sodium metal and water is given by the chemical equation below:

2Na(s) + 2H₂O(l) > 2NaOH(aq) + H₂(g)

From the equation of reaction above, 2 moles of sodium reacts with 1 mole of water to produce 2 moles of sodium hydroxide and 1 mole of hydrogen  gas.

mole ratio of sodium and hydrogen gas is 2:1

molar mass of sodium =23 g/mol:

number of moles of sodium present in 15.3 g = mass/molar mass

number of moles of sodium present in 15.3 g = 15.3 g/ 23 g/mol = 0.665 moles

number of moles of hydrogen gas produced = 0.665 * 1/2 = 0.333 moles

Therefore, number of moles of hydrogen gas produced when 15.3 g of sodium reacts with water is 0.333 moles

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

the answer for sodium is 0.186

the answer for rubidium is 0.251