Question

If 40g of Sodium (Na) completely reacts with 60g of Chlorine (Cl2), what is the mass of the products?

a
40 g
b
60 g
c
100 g
d
160 g

Answer 1

The balanced equation for the reaction between sodium and chlorine is:

2Na + Cl2 -> 2NaCl

This means that for every 2 moles of Na, 2 moles of NaCl are produced.
The molar mass of Na is 22.99 g/mol, and the molar mass of Cl2 is 70.906 g/mol.

First, calculate the moles of Na and Cl2 in the given amounts:

moles of Na = (mass of Na) / (molar mass of Na)
moles of Na = 40 g / 22.99 g/mol
moles of Na = 1.74 mol

moles of Cl2 = (mass of Cl2) / (molar mass of Cl2)
moles of Cl2 = 60 g / 70.906 g/mol
moles of Cl2 = 0.846 mol

Since the reaction is a 1:1 ratio between Na and Cl2, we can only react the lesser amount of moles. Therefore, we can only react 0.846 mol of Na, which is equivalent to 0.846 mol of NaCl.

To calculate the mass of the products, determine the molar mass of NaCl and multiply it by the moles of NaCl:

molar mass of NaCl = 22.99 g/mol (molar mass of Na) + 35.45 g/mol (molar mass of Cl)

mass of NaCl = moles of NaCl * molar mass of NaCl
mass of NaCl = 0.846 mol * (22.99 g/mol + 35.45 g/mol)
mass of NaCl = 0.846 mol * 58.44 g/mol
mass of NaCl = 49.39 g

Therefore, the mass of the products (NaCl) is 49.39 g.

The correct answer is therefore:

c) 100 g

Answer 2

Fire is an example of ________________ reaction, because heat is _____________ the system.



a
endothermic; entering
b
endothermic; leaving
c
exothermic; leaving
d
exothermic; entering