Atoms and Molecules — Science STD 9 — Question

In a sample of ethyl ethanoate (CH₃COOC₂H₅) the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it?

Formula unit mass of CaCO₃​ is:

Among the following, name a mixture which is used as a food:

3.42g of sucrose are dissolved in 18g of water in a beaker. The numbers of oxygen atoms in the solution are:

Which of the following elements has the same molecular mass as its atomic mass?

1. Nitrogen.
2. Neon.
3. Oxygen.
4. Chlorine.

Of the following substance which is an element, a mixture and a compound Sea water is the example of :

Which of the following statements is/ are correct:

When a crystal of potassium permanganate is placed at the bottom of water in a beaker, the water in the whole beaker turns purple on its own, even without stirring. This is an example of:

1. Distribution.
2. Intrusion.
3. Diffusion.
4. Effusion.

Which of the following can be called a suspension?

1. Milk.
2. Milk of magnesia.
3. Salt solution.
4. Vinegar.