Acids, binary

Are the acid properties of Hi what you wouid expect from this figure  

SiH4 Neither acid nor base PH3 Very weak base iCfc = 4 X 10 H2S Weak acid Kc = 9.5 X 10 HCl Strong acid 

Neither acid nor base Weak base Kfc 1.8 X 10 Weak acid Ka = 6.8 X 10  

Neither acid nor base Very weak base Kfc = 4 X 10 -2 Weak acid Ka = 9.5 X 10 Strong acid 

The periodic trends in the acid strengths of binary compounds of hydrogen and the nonmetals of periods 2 and 3 are summarized in FIGURE 16.17. 

What is the major factor determining the increase in acidity of binary acids going down a group What is the major factor going across a period  

Consider the bond between a hydrogen atom and some other generic element (which we wiUcaUY)  

The fadors affecting the ease with which this hydrogen is donated (and therefore be acidic) are the polarity of the bond and the strength of the bond. 

Bond Polarity Using the notation introduced in Chapter 9, the H—Y bond must be polarized with the hydrogen atom as the positive pole in order for HY to be acidic  

This requirement makes physical sense because the hydrogen atom must be lost as a positively charged ion (iC). A partial positive charge on the hydrogen atom facilitates its loss. Consider the following three bonds and their corresponding dipole moments  

HCl and HBr have weaker bonds and are both strong acids. HF, however, has a stronger bond and is therefore a weak acid, despite the greater bond polarity of HF. 

---

Step 1 If the compound is a binary acid in solution, add hydro.. . ic acid to the root of the element s name. 

H->0 < H->S < H->Se < H-,Te. Because bond strengths decrease and acid strength increases down the group, it appears that bond strength dominates the trend in acid strength in these two sets of binary acids. 

To balance a chemical equation, the chemical formulas for the reactants are first written on the left-hand side of the equation. For example, in the reaction between hydrochloric acid and sodium hydroxide, the chemical formulas are HCl and NaOH, respectively. Remember that if an acid starts with the prefix hydro-, it is a binary acid. That means that hydrochloric acid is made up of only two... 

Binary acid An acid composed of only two elements. 

Recall that, because of the strong H-F bond, hydrofluoric acid is a weak acid with a small acid dissociation constant Ka of 6.8 x 10-4. In contrast, the other binary acids of the halogen family—HC1, HBr, and HI—are strong acids that completely dissociate in water.) The fluorosilicic acid produced, H2SiF6, is a water-soluble substance with a structure as in Fig. 6.3.1. 

Many hydrogen compounds are acids. Acids require a different system of nomenclature than other compounds. There are two types of acids binary acids and ternary acids. All acids include the word acid in their name. Binary acids contain only two elements one of which is hydrogen and the other a nonmetal. When naming binary acids, the prefix hydro- appears before the root name of the nonmetal, and there will be an -ic suffix. As an acid, H2S would be hydrosulfuric acid. We used H2S to illustrate the fact that there can be two possible names, hydrogen sulfide or hydrosulfuric acid. If your instructor does not specify which name to use, either is correct. Technically, the name hydrosulfuric acid only applies to aqueous solutions of H2S, H2S(aq). 

The binary acids of non-metals exhibit periodic trends in their acid strength, as shown in Figure 8.5. Two factors are responsible for this trend the electronegativity of the atom that is bonded to hydrogen, and the strength of the bond. 

The binary acids show periodic trends, which are related to electronegativity and bond strength. 

The two most common types of acids you encounter in a basic chemistry class are binary acids and oxy-acids ... 

Binary acids You can easily recognize a binary acid when you see hydrogen bonded to a nonmetallic element or polyatomic ion without oxygen present. 

J 1 Oxy-acids Oxy-acids contain hydrogen bonded to a polyatomic ion containing oxygen. To name a binary acid (no oxygen), use the following steps ... 

Hydrobromic acid. HBr is a binary acid it doesn t contain oxygen, so it isn t an oxy-acid. You begin by writing hydro-. Next, change the ending of the anion name, bromine, to -ic and write bromic after hydro- Write acid at the end, and you re done ... 

Write the proper names for the following binary acids ... 

Does the formula begin with an H If so, use the rules presented ecirlier in Addressing Acids. Be sure to identify whether the compound is a binary acid or an oxy-acid. If the compound doesn t begin with an H, move along to Question 2. 

Identify the anion for each oxy-acid from the polyatomic ion chart in Table 6-1. If the polyatomic ion ends in -ate, change the ending to -ic. If the polyatomic ion ends in -/Ye, change the ending to -ous. Write acid at the end of the name. (Don t begin with hydro- These aren t binary acids.)... 

For bases of binary acids (H X) of elements in the same Group, the larger the basic site X, the more spread-out is the charge. Compared bases must have the same charge. 

For like-charged bases of binary acids in the same period, the more unshared pairs of electrons the basic site has. the more delocalized is the charge. 

Inert metals (Cu, Hg, Ag, Pt, Au) do not react with binary acids (HCI, HBr...). Cu, Hg and Ag can react with strong oxyacids such as HNO3 and H2SO4. For example,... 

Double Decomposition.—Many binary compounds may be regarded as salts of definite binary acids as well as compounds formed by the union of two elements. Among such compounds are the metallic halides, sulfides, selenides, tellurides, and peroxides. Many salts of these acids may be made by neutralizing a soluble base with the appropriate acid a much larger number may be made by the method of double decomposition (Exercise 15). 

For binary acids of elements in the same row of the periodic table, changes in the H-A bond strength are smaller, and the polarity of the H-A bond is the most important determinant of acid strength. The strengths of binary acids of the second-row elements, for example, increase as the electronegativity of A increases ... 

Periodic trends in the strength of binary acids are summarized in Figure 15.10. 

Binary acids, acids that are formed from a hydrogen ion bonding to a monatomic anion, are named by placing the term hydro- in front of the root of the anion ending in -ic. For instance, HC1 is called hydrochloric acid. 

There are a few trends about acid strengths that you should be familiar with. If you consider the acid HA, the bond between H and A will have to be broken in order for the hydrogen ion to be donated. For binary acids (those containing only hydrogen and a nonmetallic element), there are two main factors that determine the ease of this process the polarity of the bond between H and A and the size of A. The factors can be summarized as follows ... 

---