# Identify the value for standard pressure

Sum of the atomic masses of all atoms in a compound 4. What do we call the number of atoms of an element equal to the number of atoms in exactly 12. 0 grams of carbon-12? Mole or Avogadro’s number 5. How many atoms are in a sample of an element whose mass is numerically equal to the atomic mass of that element? 6. 02×1023 6. For what substance do we use formula units? Ionic compound . At STP, equal volumes of different gases contain what? Same number of particles = 1 mole 8. Identify the value for standard temperature. 25C 9. Identify the value for standard pressure. 1 atm 10. Identify the number used to express molar volume of a gas at STP. 22. 4 L 11. What does the sum of the percentages in the percentage composition of a substance equal? 100% 12. Define empirical formula. Identify the empirical formula of a compound with molecular formula of C2Cl6 EF = smallest whole number ratio of the atoms in a compound CCl3 13. Define molecular formula.

The procedure produces 0. 36 grams of hydrogen (H), 3. 73 grams of phosphorus (P), and 7. 69 grams of oxygen (O). Determine the percentage composition of the compound. H = 3. 1% P = 32% O = 65% 21. A sample of a molecular compound was analyzed and found to contain 9. 09 grams carbon (C), 1. 52 grams of hydrogen (H), and 14. 40 grams of fluorine (F). a. Determine the empirical formula of the compound. CH2F b. Given the added information that the molar mass of the compound is 66. 0 g/mol, determine the molecular formula of the compound. C2H4F2