What does below chemistry rebus means?

Why are all black people so quick ?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.

What is the below Rebus indicate?

There are two beautiful yet remote islands in the South Pacific. The Islanders born on one island always tell the truth, and the Islanders from the other island always lie.
You are on one of the islands and meet three Islanders. You ask the first which island they are from in the most appropriate Polynesian tongue, and he indicates that the other two Islanders are from the same island. You ask the second Islander the same question, and he also indicates that the other two Islanders are from the same island.
Can you guess what the third Islander will answer to the same question?

Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

Joseph organises an exotic office New year party at the beach to his important fellow employees.

Following are the important people that will come to the party

1. Joseph

2. Joseph 2 girlfriends- Carol Vanstone and Tracey Hughes

3. The sales head Clay Vanstone.

4. Clay Vanstone 2 associates.

5. Mr. Jeremy and his Secret Tab.

They all need to cross a small river to reach the beach, however, Joseph has got just one boat.

There are few rules for crossing the river.

1. The capacity of the boat is limited to just two people.

2. Clay Vanstone associates will not stay with Joseph without Clay Vanstone.

3. Carol Vanstone and Tracey Hughes will not stay with the Clay Vanstone without Joseph.

4. Mr. Jeremy would never leave the Secret Tab alone.

5. Secret Tab counts as a person.

6. Only Joseph, Clay Vanstone or Mr. Jeremy can drive the boat.

7. The two girlfriends Carol Vanstone and Tracey Hughes will not stay with the Clay Vanstone without Joseph.

8. No Associates would stay with Joseph without their Clay Vanstone.

9. Mr.Jeremy will not leave the Secret Tab alone.

Katrina wants to go on a date and prefers her date to be tall, dark and handsome.

Of the preferred traits - tall, dark and handsome - no two of Shahrukh, Ajay, Salman and Akshay have the same number.
Only Shahrukh or Akshay is tall and fair.
Only Ajay or Salman is short and handsome.
Shahrukh and Salman are either both tall or short.
Ajay and Akshay are either both dark or both fair.
Who is Katrina's date?

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?