Answer:
Percentage yield = 0.49 × 10² %
Explanation:
Given data:
Actual yield of SO₂ = 4.309 ×10² g
Theoretical yield of SO₂ = 8.78 ×10² g
Percentage yield = ?
Solution:
Chemical equation:
2NiS₂ + 5O₂ → 2NiO + 4SO₂
Percentage yield:
Percentage yield = actual yield / theoretical yield × 100
Percentage yield = 4.309 ×10² g / 8.78 ×10² g × 100
Percentage yield = 0.491 × 100
Percentage yield = 49.1%
In scientific notation:
Percentage yield = 0.49 × 10² %
Answer:
the answer D) will cause milk to go bad
B) land cools off much faster than water (creating a air region of high density above land and lower density above sea)
Answer: Compound
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water 

Thus as it give that the red sample on being heated, a gas is released and a blue powder is left after the heating. Thus the given sample is a compound.