Chemistry is the study of the substances that make up matter. It looks at their properties, how they react with each other, and how these reactions can create new substances.
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Question 251:
Which of the following alkaline metals react more quickly spontaneously with water?
Options:
A) Calcium
B) Beryllium
C) Magnesium
D) Strontium
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The correct answer is A .
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Question 252:
The option above shows the PH changes for the titration of a
Options:
A) strong acid versus strong base
B) weak acid versus strong base
C) strong acid versus weak base
D) weak acid versus weak base
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The correct answer is A .
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Question 253: If atom X with six electrons in its outermost shell combines with atom Y with one electron in its outermost shell to form an ionic compound, then?
Options:
A) six atoms of X will combine with one of Y
B) two atoms of X will combine with six of Y
C) one atom of X will combine with two of Y
D) two atoms of X will combine with one of Y
E) one atom of X will combine with six of Y
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The correct answer is C .
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Question 254: In the extraction of aluminum from purified bauxite by electrolysis, cryolite is used because
Options:
A) it makes bauxite a better conductor of electricity
B) it makes bauxite melt at a lower temperature
C) it makes aluminium purer
D) it prevents aluminium from getting oxidized
E) it protects the carbon electrodes used in the process
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The correct answer is B .
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Question 255: Chlorination of water for town supply is carried out to
Options:
A) make the water colourless
B) remove germs from the water
C) make the water tastedful
D) remove odour from the water
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The correct answer is B .
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Question 256: Which group of elements forms hydrides that are pyramidal in structure?
Options:
A) III
B) IV
C) V
D) VI
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The correct answer is C .
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Question 257:
A radioactive nucleus has a half-life of 20 years, starting with 100,000 particles, how many particles will be left exactly at the end of 40 years
Options:
A) 75,000 particles
B) 35,000 particles
C) 25,000 particles
D) 50,000 particles
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The correct answer is C .
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Question 258: The electron configuration of two elements with similar chemical properties are represented by?
Options:
A) 1s22s22p5 and 1s22s22p4
B) 1s22s22p4 and 1s22s22p63s1
C) 1s22s22p63s1 and 1s22s1
D) 1s22s22p4 and 1s22s1
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The correct answer is C .
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Question 259: Cr2O7 + 6Fe2+ + 14H+ → 2Cr3+ +6Fe3+ + 7H2O. In the above , the oxidation number of chromium changed from?
Options:
A) +7 to +3
B) +6 to +3
C) +5 to +3
D) -2 to +3
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The correct answer is A .
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Question 260: Which of the following changes is physical?
Options:
A) Adding iron filing to aerated water
B) Adding sodium metal to water
C) Cooling a solution of Iron (II) sulphate to obtain the hydrated salt
D) Cooling water to obtain ice
E) Burning the domestic gas (Utilgas) for cooking
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The correct answer is D .