This is the teacher's method. Step 1 find the mass of the reduction tube
Step 2 add some of the lead oxide to the reduction tube
Step 3 find the mass of the reduction tube and lead oxide
Step 4 pass hydrogen gas over the lead oxide and ignite the hydrogen at the hole
Step 5 heat the lead oxide strongly for 10 minutes
Step 6 keep passing hydrogen through the reduction tube until the tube and contents are cool Step 7 find the new mass of the reduction tube and its contents
(i) Give a reason why hydrogen is passed through the reduction tube until the tube and contents are cool.