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- Question
How many electrons are there in Na+
Options- A. 1
- B. 10
- C. 11
- D. 12
- Correct Answer
- 10
- 1. 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
- 2. Which one of the following elements is essential for construction is nuclear reactors
Options- A. Cobalt
- B. Nickel
- C. Zirconium
- D. Tungsten Discuss
- 3. The absolute value of charge on electron was determined by
Options- A. J.J.Thomson
- B. R.A. Millikan
- C. Rutherford
- D. Chadwick Discuss
- 4. Sodium carbonate crystal lose water molecules this property is called
Options- A. hygroscopy
- B. deliquescence
- C. efflorescence
- D. None of these Discuss
- 5. Which one of the following substances does not have a melting point
Options- A. bromine
- B. sodium chloride
- C. mercury
- D. glass Discuss
- 6. ' 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
- 7. Which one of the following elements is the poorest conductor of heat
Options- A. sodium
- B. lead
- C. zinc
- D. mercury Discuss
- 8. When water freezes its density
Options- A. decreases
- B. remains constant
- C. increases
- D. become zero Discuss
- 9. 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
- 10. What is the third most common gas found in the air we breathe ?
Options- A. Argon
- B. Neon
- C. Carbondioxide
- D. Hydrogen Discuss
Chemistry problems
Search Results
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: R.A. Millikan
Correct Answer: efflorescence
Correct Answer: glass
Correct Answer: Cigarette lighters
Correct Answer: lead
Correct Answer: decreases
Explanation:
When 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.
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.
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