C. Incorrect! These are the correct symbols, but the charges must be balanced. D. Correct! The charges are balanced in this formula.

Transcription

1 SAT Chemistry - Problem Drill 07: Writing Chemical Formulas No. 1 of Which of the following is correct for sodium oxide? (A) SO (B) S 2 O (C) NaO (D) Na 2 O (E) NaO 2 Sodium is symbolized with Na. Sodium is symbolized with Na. These are the correct symbols, but the charges must be balanced. D. Correct! The charges are balanced in this formula. These are the correct symbols, but the charges must be balanced. This is a binary ionic compound. Sodium is Na + Oxide is O 2- Na + Na + O 2- would give a neutral compound: Na 2 O The correct answer is (D).

2 No. 2 of Which of the following is the correct formula for carbonic acid (A) HCO 3 (B) H 2 CO 3 (C) H 3 CO 3 (D) H 6 CO 3 (E) None of these These are the correct ions, but the charges need to be balanced. B. Correct! The charges are correctly balanced in this compound. The charges are not balanced in this choice. The 3 in the polyatomic ion is not multiplied by the -2 polyatomic charge. Look more closely. There is a correct answer. This is an acid. ic acids come from -ate polyatomic ions. Carbonate is CO 3 2- Acids begin with H + H + H + CO 3 2- would result in a neutral compound: H 2 CO 3 The correct answer is (B).

3 No. 3 of Which of the following is correct for Ammonium phosphate? (A) NH 4 PO 4 (B) (NH 4 ) 3 PO 4 (C) NH 4 (PO 4 ) 3 (D) (NH 4 ) 12 PO 4 (E) None of the above You must balance the charges. B. Correct! The charges are correctly balanced. The charges aren t balanced. Don t multiply the charge by a subscript within the polyatomic ion. Look more closely there is a correct option. This is a polyatomic ionic compound. Ammonium is NH 4 1 Phosphate is PO You do not multiply the polyatomic ion s subscript by its charge. NH 4 + NH 4 + NH 4 + PO 4 3- would result in a neutral compound: (NH 4 ) 3 PO 4 The correct answer is (B).

4 No. 4 of Which of the following is correct for copper (II) hydroxide? (A) Cu 2 OH (B) CuOH 2 (C) Cu(OH) 2 (D) Co 2 OH (E) Co(OH) 2 The roman numeral doesn t mean there are two copper atoms, it means the copper ion has a charge of +2. When using a subscript with a polyatomic ion, make sure to use parenthesis. C. Correct! The charges are correctly balanced. The symbol for copper is Cu The symbol for copper is Co This is a polyatomic ionic compound. The roman numeral gives the cation charge. Copper (II) is Cu 2+ Hydroxide is OH - Cu 2+ OH - OH - would give a neutral compound. Remember to use parenthesis with polyatomic ions: Cu(OH) 2 The correct answer is (C).

5 No. 5 of Which of the following is correct for silicon dioxide? (A) SiO 2 (B) Si 2 O (C) SiO (D) SO 2 (E) S 2 O A. Correct! The Di indicates there are two oxygen atoms. The di is with the oxygen, not the silicon. Di means two oxygen atoms. The symbol for silicon is Si. The symbol for silicon is Si. This is a binary covalent compound. Do not worry about charges as they don t form charges just write what the compound says, using the prefixes to designate subscripts. (Remember mono is not used on the first element). Silicon is Si Dioxide is O 2 The correct answer is (A).

6 No. 6 of Which of the following is correct for iron (III) carbonate? (A) Fe 3 CO 3 (B) Fe 3 (CO 3 ) 2 (C) Fe 2 (CO 3 ) 2 (D) Fe 2 CO 3 (E) Fe 2 (CO 3 ) 3 The roman numeral indicates the charge of the iron ion, not the number of atoms. The roman numeral indicates the charge of the iron ion, not the number of atoms. The charges are not balanced in this choice. The charges are not balanced in this choice. E. Correct! The charges are balanced in this choice. This is a polyatomic ionic compound. The roman numerals give the charge of the cation. Iron (III) is Fe 3+ Carbonate is CO 3 2- Fe 3+ Fe 3+ CO 3 2- CO 3 2- CO 3 2- is a neutral compound. Remember to use parenthesis with polyatomic ions. Fe 2 (CO 3 ) 3 The correct answer is (E).

7 No. 7 of Which of the following is hydrosulfuric acid? (A) HS (B) H 2 S (C) H 2 SO 3 (D) H 2 SO 4 (E) None of the above You need to balance the charges. B. Correct! A hydro acid does not contain oxygen and the charges are balanced. A hydro acid does not contain oxygen. A hydro acid does not contain oxygen. Look again there is a correct option in the list. hydro acids do not contain oxygen. sulfuric is S 2- Acids begin with H + H + H + S 2- is a neutral compound: H 2 S The correct answer is (B).

8 No. 8 of Which of the following is dinitrogen tetraoxide? (A) Ni 2 O 4 (B) N 2 O 4 (C) Ni 2 O 5 (D) N 2 O 5 (E) None of the above The symbol for nitrogen is N. B. Correct! The symbol for nitrogen is "N". The symbol for nitrogen is N. tetra stands for 4 atoms of oxygen. Look more closely there is a correct choice. This is a binary covalent compound. They do not form charges. Use the prefixes to indicate subscripts. Dinitrogen is N 2 Tetraoxide is O 4 N 2 O 4 The correct answer is (B).

9 No. 9 of Which of the following is calcium fluoride? (A) Ca 2 F (B) CaF (C) CaF 2 (D) C 2 F (E) CF 2 The charges aren t balanced. The charges aren t balanced. C. Correct! The +2 charge of the calcium is balanced with 2 fluoride ions with -1 charge each. The symbol for calcium is Ca. The symbol for calcium is Ca. This is a binary ionic compound. Calcium is Ca 2+ Fluoride is F - Ca 2+ F - F - is a neutral compound: CaF 2 The correct answer is (C).

10 No. 10 of Which of the following is phosphoric acid? (A) HP (B) H 3 P (C) H 3 PO 4 (D) H 12 PO 4 (E) None of them Acids without hydro contain oxygen. Acids without hydro contain oxygen. C. Correct! The ic acid came from the ate anion. Don t multiply the charge of a polyatomic ion by the subscript within the ion. Look more closely - there is a correct answer. This is an acid. ic acids come from ate polyatomic ions. Phosphate is PO 4 3- Acids begins with H + H + H + H + PO 4 3- is a neutral compound: H 3 PO 4 The correct answer is (C).