Final answer:
To make 2 kg of brass with a zinc to copper ratio of 3:7, you will need 600 grams of zinc.
Step-by-step explanation:
To find the mass of zinc needed to make 2 kg of brass, we first need to determine the fraction of the brass that is zinc. Since the ratio of zinc to copper in the brass is 3:7, the total ratio is 10 parts. Therefore, zinc makes up 3/10 of the brass and copper makes up 7/10. To find the mass of zinc, we multiply the total mass of brass (2 kg) by the fraction of zinc (3/10):
Mass of zinc = 2 kg (3/10) = 0.6 kg = 600 g
So, in order to make 2 kg of brass, you will need 600 grams of zinc.