Chemistry Questions & Answers - Free Online Practice

1,566.

What is the change in the oxidation number of 1^- in the reaction represented by the following equation? 51 ^-1_(aq) + 6H⁺_(aq) + 1O^-_3(aq) → 31_2(g) + 3H₂O_(l)

-5 to -3

-1 to 0

+ 5 to + 0

-1 to + 2

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Correct answer is B

No explanation has been provided for this answer.

1,567.

Which of the following statements is true of an endothermic reaction? I. Heat is absorbed from the surrounding II. The heat content of the products is more than that of the reactants III. The enthalpy change is positive IV. The surrounding is at a lower temperature than the system.

l only

l and ll only

l,ll and lll only

l, ll, lll and lV

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Correct answer is C

For an endothermic reaction; heat flows from the surroundings to the system( but that doesn't make the surroundings to be at a lower temperature than the system) meaning the surroundings are at a higher temperature than the system. The system's enthalpy change, i.e. ΔH is positive or > 0. The heat content of the product is more than that of the reactant.

1,568.

The condensation of several amino acid molecules gives

long chain alkanoic acids

secondary alkanols

alkanoates

proteins

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Correct answer is D

No explanation has been provided for this answer.

1,569.

When ammonium trioxocarbonate (IV) solution is added to separate solutions of calcium, zinc and sodium salt precipitate could be formed in the case of

calcium only