Where is the rest of the question?
Answer:

Explanation:
A marble is not a very large object, so a smaller graduated cylinder is a better choice. A 100 milliliter graduated cylinder is not needed to measure the volume of a small marble, so a 25 milliliter graduated cylinder is the best option.
Answer:
67.91 g of CuCl2; 32.09 g of Cu.
Explanation:
The two masses add to 100.0 g, the initial amount of starting material, demonstrating the law of conservation of matter.
The correct answer is C: Calcium carbonate in water is a solution
Answer:
pH = 3.65
Explanation:
given data
pKa of HNO2 = 3.40
nitrous acid (HNO2) = 0.110 M
NaNO2 = 0.200 M
to find out
What is the pH
solution
we get here ph for acidic buffer that is express as
pH = pKa + log(salt÷acid) ........................1
put here value and we get
pH = 3.40 + log(0.200÷0.110)
pH = 3.65