Hydrogen and its compounds explores the simplest element in the universe, its placement in the periodic table, and key compounds like water and hydrides.
An element X has four electrons in its outermost orbit. What will be the formula of its compounds with Hydrogen?
Correct Answer:
(D)
XH4
The compounds of element X which has four electrons in its outermost orbit will be XH4.
H
|
H – X – H → XH4
|
H
Ques: 2
According to weight, the percentage of Hydrogen in water (H2O), is –
Correct Answer:
(D)
11.11 %
Percentage of composition is the percent by mass of each element present in a compound.
In Water, H2O = 2+ 16 = 18 g/mol
No. of Hydrogen atoms present in Water = 2
∴ Percentage of Hydrogen in water = 2/18*100=11.11%
Ques: 3
One mole of hydrogen gas burns in excess of oxygen to give 290 KJ of heat. What is the amount of heat produced when 4g of Hydrogen gas is burnt under the same conditions?
Correct Answer:
(C) 580 KJ
1 Mole of H2 (Hydrogen) = 2 gm
∴ Energy released by 4 gm = 290×2 = 580 KJ
Ques: 4
Burning of hydrogen produces –
Correct Answer:
(D)
Water
Hydrogen gas is highly flammable and burns in air at a very wide range of concentrations between 4% to 75% by volume. Hydrogen gas cannot burn in absence of air. But by burning with oxygen it produces water.
Ques: 5
Which one of the following fuels causes minimum air pollution?
Correct Answer:
(B) Hydrogen
Hydrogen is the purest combustion fuel. Water is generated from burning of hydrogen. While coal, kerosene oil and diesel are known as fossil fuel or carbonic fuel which generates carbon dioxide and many other harmful gases when it burns.
Ques: 6
Who among the following discovered heavy water?
Correct Answer:
(B) H.C. Urey
Harold Clayton Urey, an American chemist discovered deuterium and heavy water in 1931. He was awarded Nobel Prize in Chemistry in 1934 for his discovery.
Ques: 7
Heavy water has molecular weight :
Correct Answer:
(B) 20
Heavy water (D2O), also called deuterium oxide, is water composed of deuterium, a hydrogen isotope with mass double that of ordinary hydrogen. Thus, heavy water has a molecular weight of about 20, whereas the ordinary water has a molecular weight of about 18.
Ques: 8
Consider the following statements :
Hard water is not suitable for
1. Drinking
2. Washing clothes with soap
3. Use in boilers
4. Irrigating crops
Which of these statements are correct ?
Correct Answer:
(D)
1, 2, 3 and 4
Hard water is described as 'hard' due to the presence of highly dissolved minerals specifically sulphates and chlorides of calcium and magnesium. Hard water is salty and therefore not used for drinking. It is very difficult to wash clothes with hard water as it requires more soap and leaves a messy scum that cannot be washed out easily. When hard water is boiled at home or in industries, it leaves deposits of magnesium salts. These deposits reduce the efficiency of boilers, kettles and pipes and can cause blockages and even burst of the boilers. If salt level increases in irrigation water, it becomes harder for lawns and landscape plant to take up water even though the soil is moist. Hard water blocks the Xylem tissues of the plants and thus not suitable for irrigation.
Ques: 9
The pH-value for water is –
Correct Answer:
(B) Nearly 7
The pH value of pure water is 7. Pure water is neutral by nature. The solution with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline.
Ques: 10
Which is the purest form of water?
Correct Answer:
(C) Rainwater
Among the given options rainwater is the purest form of water. The water on the earth is mixed with alkaline and acidic materials that make the water impure.