1. Seawater contains approximately 3.5%NaCl by mass and has a density of 1.02 g/
ID: 497425 • Letter: 1
Question
1. Seawater contains approximately 3.5%NaCl by mass and has a density of 1.02 g/mL. What volume of seawater contains 9.0 g of sodium?
2. Methanethiol (CH4S) has a disagreeable odor and is often a component of bad breath. When methanethiol is burned, the sulfur reacts with oxygen to form SO2. What mass of SO2 is formed upon the complete combustion of 1.87 g of methanethiol?
3. Amylose is a "polysaccharide" that plants use to store energy. It is made of repeating subunits of C6H10O5.
a. A particular amylose molecule has 2113 of these subunits, what is its molecular formula?
b. What is its molar mass?
c. What is the empirical formula for amylose? Express your answer as a chemical formula
4. How many atoms are in 9 mol of atoms?Express your answer using four significant figure
Explanation / Answer
1.
3.5 grams NaCl in 100 g of solution
Mass solution that contains 9 g = 100*9 / 3.5 = 257.14 g
Volume = 257.14 g / 1.02 g/mL =252.1 mL
2.
The complete combustion of Methanethiol (CH4S) can be given as:
CH4S + 3O2 = CO2 + 2H2O + SO2
1 mol 1 mol
1.87 g of methanethiol (CH4S) = 1.87/ 48.11 = 0.0388 mol of CH4S
Mol of SO2 formed = 0.0388
So mass of SO2 formed = 0.0388 * 64.066 = 2.49 g
3.
C6H10O5 for one subunit.
a)
Multiply every number with 2113. And we will need one oxygen to join two subunits.
Oxygen No = 2113 – 1 = 2112
C12678H21130O12677
b) Molar Mass of C is 12.01, H is 1.01 and of O is 16
Multiply molar mass with number of atoms of each type.
C = 12.01 * 12678 = 152271.65 g/mol
H = 1.01 * 21130 = 21296.93 g/mol
O = 16 * 12677 = 202824.39 g/mol
Total molar mass is 366392.96 g/mol
c) C14H26O11
4.
Each mole of atom contains 6.22 * 10^23 number of atoms.
9 mole will contain
6.022*10^23 * 9 = 5.419 *10^24 atoms
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