S11-HW1-CH4 - HOMEWORK WEEK 1 CHAPTERS 4 16 010 An ionic binary compound NaCl Al(NO3)3 a molecular binary compound H2O HF 2.18 See Hints sheet for

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HOMEWORK WEEK 1, CHAPTERS 4, 16 010. An ionic binary compound: NaCl, Al(NO 3 ) 3 ; a molecular binary compound: H 2 O, HF. 2.18. See Hints sheet for instructions Ionic compound: only picture A Molecular compound: Picture C – could be CO 2 ; Picture E – could be liquid water; Picture G – again water, in the vapor this time. 020. A strong electrolyte is a soluble species that exists in solution almost entirely as ions. An example is NaCl. When NaCl dissolves in water, it dissolves almost completely to give Na + and Cl ions. A weak electrolyte is a species that dissolves in water to give a relatively small percentage of ions. An example is NH 3 . When NH 3 dissolves in water, it reacts very little with the water, so the level of NH 3 is relatively high, and the level of the NH 4 + and OH ions is relatively low. For us, strong electrolytes include strong acids, soluble strong bases and (other) soluble ionic compounds. And weak electrolytes are our weak acids and weak bases (including water). 4.5 A spectator ion is an ion that does not take part in the reaction. In the following reaction of NaOH with HCl, written in total ionic form, the Na + and Cl - are spectator ions: Na + (aq) + OH - (aq) + H + (aq) + Cl - (aq) Na + (aq) + Cl - (aq) + H 2 O(l) Note that they appear in identical form on both sides of the equation. 030. The answer is (e), HF( aq ) + OH ( aq ) F ( aq ) + H 2 O( l ). Reasoning: We write weak acids in their molecular form, i.e. HF(aq). The strong base, KOH, is split into its ions, K + (aq) + OH - (aq). The product species KF, which is also an ionic compound, is also split into its ions. K + is a spectator and is canceled from both sides. Note that the N.I.E. has the form of a Bronsted Lowry acid-base reaction. Response (a) is the equation for a strong acid-strong base reaction. (b) is a poor version of (a) – KOH should break into ions. c) has many problems, including that it is not balanced. (d) KF should be broken into its ions, then the spectator K + cancelled. 040. The answer is (d), MgCl 2 . Reasoning: (c) HClO 4 contains a Cl atom covalently bonded to 4 O atoms. This will yield the ClO 4 - ion in solution, but no Cl - ions. For our purposes, the only covalent bond which breaks in water is that involving an acidic H atom (e.g. HCl). (b) PbCl 2 has low solubility (see Table 4.1), so yields very few ions in solution. NaCl (ionic), MgCl 2 (ionic) and HCl (molecular, but a strong acid and strong electrolyte) split completely into ions, Na + + Cl - , Mg 2+ + 2 Cl - , and H + (or H 3 O + ) + Cl - . Thus all yield plenty of Cl - ions, but MgCl 2 yields the largest number.
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4.33 a. All the (aq) species are strong electrolytes (ionic or strong acid), so they split completely into ions:
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This note was uploaded on 02/20/2011 for the course CHEM 110 taught by Professor Dr.huston during the Spring '06 term at Pittsburgh.

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S11-HW1-CH4 - HOMEWORK WEEK 1 CHAPTERS 4 16 010 An ionic binary compound NaCl Al(NO3)3 a molecular binary compound H2O HF 2.18 See Hints sheet for

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