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How many moles are contained in 1.20 x 1025 molecules of NH3?

Chemistry

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Answer

C

helium nuclei

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Here are the answers to the questions:

14. Alpha particles are represented by
Alpha particles are essentially the nuclei of helium atoms, consisting of two protons and two neutrons.
The correct answer is C. helium nuclei.

15. The acid which is found in butter is
Butyric acid (also known as butanoic acid) is a carboxylic acid that gives butter its characteristic smell and taste.
The correct answer is C. butyric acid.

16. How many moles are contained in 1.20×10251.20 \times 10^{25} molecules of NH3\text{NH}_3?

  1. Recall Avogadro's number.

    Avogadro's number is 6.022×10236.022 \times 10^{23} molecules/mol.

  2. Calculate the number of moles.

    Moles=Number of moleculesAvogadro’s number\text{Moles} = \frac{\text{Number of molecules}}{\text{Avogadro's number}} Moles=1.20×1025 molecules6.022×1023 molecules/mol\text{Moles} = \frac{1.20 \times 10^{25} \text{ molecules}}{6.022 \times 10^{23} \text{ molecules/mol}} Moles=19.927 mol\text{Moles} = 19.927 \text{ mol}

    Rounding to three significant figures, this is 19.9 moles.
    The correct answer is D. 19.9 moles.

    17. In the electrolysis of aqueous common salt solution, the substance produced at the cathode is
    Aqueous common salt solution contains Na+\text{Na}^+, Cl−\text{Cl}^-, H+\text{H}^+, and OH−\text{OH}^- ions. At the cathode (negative electrode), reduction occurs. Both Na+\text{Na}^+ and H+\text{H}^+ (from water) can be reduced. However, water has a higher reduction potential (is more easily reduced) than Na+\text{Na}^+ in aqueous solution.
    The relevant half-reaction at the cathode is:

    2H2O(l)+2e−⟶H2(g)+2OH−(aq)2\text{H}_2\text{O}(l) + 2\text{e}^- \longrightarrow \text{H}_2(g) + 2\text{OH}^-(aq)

    Therefore, hydrogen gas is produced.
    The correct answer is D. hydrogen gas.

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