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- Question
When water freezes its density
Options- A. decreases
- B. remains constant
- C. increases
- D. become zero
- Correct Answer
- decreases
ExplanationWhen water freezes its density decreases.
Water at ordinary temperatures contracts and increases in density as it is cooled, like most substances. But at about 4°C it reaches a maximum density and then decreases in density as it approaches the freezing point.
- 1. Which one of the following elements is the poorest conductor of heat
Options- A. sodium
- B. lead
- C. zinc
- D. mercury Discuss
- 2. ' Misch metal ' is widely used in manufacture of which of the following
Options- A. Material of car brake
- B. Smoke detectors
- C. Cigarette lighters
- D. Emergency lights Discuss
- 3. How many electrons are there in Na+
Options- A. 1
- B. 10
- C. 11
- D. 12 Discuss
- 4. An atom has 7 electrons in its M - shell and contains 18 neutrons in its nucleus. What is its mass number
Options- A. 25
- B. 27
- C. 35
- D. 43 Discuss
- 5. Which one of the following elements is essential for construction is nuclear reactors
Options- A. Cobalt
- B. Nickel
- C. Zirconium
- D. Tungsten Discuss
- 6. How many moles are there in 140g of Si (atomic mass of silicon is 28)
Options- A. 5
- B. 10
- C. 28
- D. 140 Discuss
- 7. What is the third most common gas found in the air we breathe ?
Options- A. Argon
- B. Neon
- C. Carbondioxide
- D. Hydrogen Discuss
- 8. The metal which reacts most violently with with cold water is
Options- A. calcium
- B. sodium
- C. magnesium
- D. potassium Discuss
- 9. What is the element present in urea
Options- A. C,H,O
- B. C,N,O
- C. C,N,H
- D. C,O,N,H Discuss
- 10. In known elements, the maximum number is of
Options- A. Metals
- B. Non Metals
- C. Metalloids
- D. None of these Discuss
Chemistry problems
Search Results
Correct Answer: lead
Correct Answer: Cigarette lighters
Correct Answer: 10
Correct Answer: 35
Explanation:
According to Bohr model, Each shell can occupy 2 electrons in their orbits where n=1,2,3.. for K,L,M,..
The atom has 2 electrons in k, 8 electrons in L and 7 electrons in M = 2 + 8 + 7 = 17
And given that its nucleus has 18 neutrons
=> its mass number = number of (electrons + neutrons ) = 17 + 18 = 35
Correct Answer: Zirconium
Correct Answer: 5
Correct Answer: Argon
Explanation:
The most common gas people breathe from clean air is nitrogen. Air is a mixture of gases, and the air on Earth contains about 78 percent nitrogen and about 21 percent oxygen. Argon, carbon dioxide neon, helium, methane, krypton, hydrogen and xenon are in much smaller amounts.
Correct Answer: potassium
Explanation:
Potassium reacts violently with water liberating hydrogen. The reaction is so violent that the liberated hydrogen catches fire.
Correct Answer: C,O,N,H
Correct Answer: Metals
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