Which of the following alloys has a maximum percentage of Copper ?
Correct Answer:
(B)
Bronze
Brass consists 68-71% Copper and rest is Zinc. Bronze consists 88% Copper and 12% Tin. German silver has almost 50% Copper. Gunmetal consists 85% Copper, 5% Tin, 5% Lead, 5% Zinc.
Ques:
12
Check these statements :
(i) Brass is an alloy of Copper and Zinc.
(ii) Magnetite is the main ore of Aluminium.
(iii) Mercurius Solubilis are that substance which mainly involves mercury.
(iv) Potassium Nitrate (KNO3) is a chemical used in photography.
Which of the above are true ?
Code :
Correct Answer:
(B)
(i) and (iii)
Statement (i) and (iii) are correct but statement (ii) and (iv) are wrong because Magnetite (Fe3O4) is an ore of Iron and Silver Bromide (AgBr) is used in photography.
Ques:
13
Brass gets fade colour in air due to the presence of –
Correct Answer:
(B)
Hydrogen Sulphide
Hydrogen Sulphide is responsible for fading of Brass.
Ques:
14
Combination of which substance in the alloy renders stainless steel non-magnetic ?
Correct Answer:
(C)
Nickel
Stainless steel becomes non-magnetic by combining the alloy with Nickel, while extra Carbon is mixed to gain more hardness.
Ques:
15
To make the steel hard requires increase in –
Correct Answer:
(A)
The quantity of Carbon
Steels are alloys of Iron and other elements primarily Carbon and are widely used in construction and other area. Carbon mixed in Iron as a hardening agent which strengthens Iron by distorting its crystal lattice. This distortion results in hardening.
Ques:
16
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:
17
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:
18
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:
19
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:
20
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.