Understanding Case in English Grammar

Understanding Case in English Grammar So what is this thing called case in English, anyway? And why is it important? Being pretty clueless about this aspect of grammar is pretty common: When teachers or editors discuss the importance of getting  case  right in English grammar, quizzical looks from listeners are often the result. But not to worry. Heres a simple explanation: Basically, the concept of case in English is the grammatical relationship of nouns and pronouns to other words in a sentence. In English, nouns have only one case inflection: the possessive (or genitive). The case of nouns other than the possessive is sometimes called the common case. Common case nouns are the basic word, such as dog, cat, sunset or water. Pronouns have three case distinctions: Subjective (or nominative)Possessive (or genitive)Objective (or accusative) Examples and Observations on Case Sidney Greenbaum discusses this basic subject of English grammar in Case in The Oxford Companion to the English Language (1992). Potentially, countable nouns have four case forms: two singular (child, childs), two plural (children, childrens). In regular nouns, these manifest themselves only in writing, through the apostrophe ( girl, girls, girls, girls), since in speech three of the forms are identical. The genitive [or possessive] case is used in two contexts: dependently, before a noun ( This is Toms/his bat), and independently ( This bat is Toms/his). Most personal pronouns have different forms for the dependent and independent genitive: This is your bat and This bat is yours. The genitive case forms of personal pronouns are often called possessive pronouns. A few pronouns have three cases: subjective or nominative, objective or accusative, and genitive or possessive.Andrea Lunsford gives tips on editing for case in The St. Martins Handbook (2008). In compound structures, make su re pronouns are in the same case they would be in if used alone (Jake and she were living in Spain). When a pronoun follows than or as, complete the sentence mentally. If the pronoun is the subject of an unstated verb, it should be in the subjective case (I like her better than he [likes her]). If it is the object of an unstated verb, it should be in the objective case (I like her better than [I like] him.). Robert Lane Greene talks about the disappearance of case endings in English in his book You Are What You Speak   (2011). While the stickler might see the misuse and gradual disappearance of whom as proof that education and society have been flushed down the toilet, most linguists   even though they will almost certainly use whom in their written work themselves see the pronouns replacement with who as merely another step in Englishs gradual shedding of case endings. In the era of Beowulf, English nouns had endings that showed what role they played in the sentence, as Latin did. But nearly all of them disappeared by the time of Shakespeare, and a linguist would see the death of whom as simply the conclusion of the process.

Net Ionic Equation Definition (Chemistry)

Net Ionic Equation Definition (Chemistry) There are different ways to write equations for chemical reactions. Three of the most common are unbalanced equations, which indicate the species involved; balanced chemical equations, which indicate number and type of species; and net ionic equations, which only deal with the species that contribute to a reaction. Basically, you need to know how to write the first two types of reactions to get the net ionic equation. Net Ionic Equation Definition The net ionic equation is a chemical equation for a reaction which lists only those species participating in the reaction. The net ionic equation is commonly used in acid-base neutralization reactions, double displacement reactions, and redox reactions. In other words, the net ionic equation applies to reactions that are strong electrolytes in water. Net Ionic Equation Example The net ionic equation for the reaction that results from mixing 1 M HCl and 1 M NaOH is:H(aq) OH-(aq) → H2O(l)The Cl- and Na  ions do not react and are not listed in the net ionic equation. How to Write a Net Ionic Equation There are three steps to writing a net ionic equation: Balance the chemical equation.Write the equation in terms of all of the ions in the solution. In other words, break all of the strong electrolytes into the ions they form in aqueous solution. Make sure to indicate the formula and charge of each ion, use coefficients (numbers in front of a species) to indicate the quantity of each ion, and write (aq) after each ion to indicate its in aqueous solution.In the net ionic equation, all species with (s), (l), and (g) will be unchanged. Any (aq) that remain on both sides of the equation (reactants and products) can be cancelled out. These are called spectator ions and they dont participate in the reaction. Tips for Writing the Net Ionic Equation The key to knowing which species dissociate into ions and which form solids (precipitates) is to be able to recognize molecular and ionic compounds, know the strong acids and bases, and predict the solubility of compounds. Molecular compounds, like sucrose or sugar, dont dissociate in water. Ionic compounds, like sodium chloride, dissociate according to solubility rules. Strong acids and bases completely dissociate into ions, while weak acids and bases only partially dissociate. For the ionic compounds, it helps to consult the solubility rules. Follow the rules in order: All alkali metal salts are soluble. (e.g., salts of Li, Na, K, etc. - consult a periodic table if youre unsure)All  NH4 salts are soluble.All NO3-, C2H3O2-, ClO3-, and ClO4-  salts are soluble.All Ag, Pb2, and Hg22  salts are insoluble.All Cl-, Br-, and I-  salts are soluble.All CO32-, O2-, S2-, OH-, PO43-, CrO42-, Cr2O72-, and SO32-  salts are insoluble (with  exceptions).All SO42-  salts are soluble (with exceptions). For example, following these rules you know sodium sulfate is soluble, while iron sulfate is not. The six strong acids that completely dissociate are  HCl, HBr, HI, HNO3, H2SO4, HClO4. The oxides and hydroxides of alkali (group 1A) and alkaline earth (group 2A) metals are strong bases that completely dissociate. Net Ionic Equation Example Problem For example, consider the reaction between sodium chloride and silver nitrate in water. Lets write the net ionic equation. First, you need to know the formulas for these compounds. Its a good idea to memorize common ions, but if you dont know them, this is the reaction, written with (aq) following the species to indicate they are in water: NaCl(aq) AgNO3(aq) → NaNO3(aq) AgCl(s) How do you know silver nitrate and silver chloride form and that silver chloride is a solid? Use the solubility rules to determine both reactants dissociate in water. In order for a reaction to occur, they must exchange ions. Again using the solubility rules, you know sodium nitrate is soluble (remains aqueous) because all alkali metal salts are soluble. Chloride salts are insoluble, so you know AgCl precipitates. Knowing this, you can rewrite the equation to show all the ions (the complete ionic equation): Na(aq)  Ã‚  Cl​−​​(aq) Ag​(aq)  Ã‚  NO​3​−​​(aq)  Ã¢â€ â€™Ã‚  Na​​​(aq)   NO​3​−​​(aq)  Ã‚  AgCl(s) The sodium and nitrate ions are present on both sides of the reaction and are not changed by the reaction, so you can cancel them from both sides of the reaction. This leaves you with the net ionic equation: Cl-(aq) Ag(aq) → AgCl(s)