3. After 7.9 grams of sodium are dropped into a bathtub full of water, how many grams of hydrogen gas are released? 4. Excess oxygen gas is added to 34.5 grams of aluminum and heated under pressure. How many grams of aluminum oxide are produced?

Please explain as well if possible!

Solution given:

3.

2Na=2*23g.

2O=18g.

=62g

=2 g

we have

2*23g of Na produce 2g of

Now

7.9 g of Na produce 2*7.9/(2*23)

=0.34g of

4.

we have

=3*16g*2g

4Al=4*27g

= 2*27*2g+2*16*3g

4*27g of Al produces 204g of

34.5g of Al produces 204g*34.5/(4*27)

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.