Answer:
heterogeneous mixture or a chemical mixture
Answer:
a) Step 1:

Step 2:

b) The overall balanced reaction for given process is ;

Explanation:
a)
Galena = 
Lead(II) oxide = 
Sulfur dioxide = 
Step 1:
Roasting the galena in oxygen gas to form lead(II) oxide and sulfur dioxide.
Balanced equation of step 1:
..[1]
Step 2:
Heating the metal oxide with more galena forms the molten metal and more sulfur dioxide.
Balanced equation of step 2:
..[2]
b)
For over all reaction add [1] and [2]. The overall balanced reaction for given process is ;

Yeah, it sure does
Hope this helps!
B is true because plants can only use nitrogen in the form of nitrates, no other living thing needs nitrogen therefore the percentage of nitrogen in the atmosphere is 79%
For 100m Race ,
displacement = distance covered .
divide the above equation by time t (assuming it takes t time to complete 100m race),
we get,
velocity = speed.
and for 400m race 1 lap is completed this means that racer's initial and final position coincide (or same) hence,
displacement = 0,
distance ≠0=400m.
=> displacement ≠distance.
=> velocity ≠ speed.