C. 137 37x 2. How many significant figures are there in each the following numbe

Question

C. 137 37x 2. How many significant figures are there in each the following numbers? 6 pts) a. 2000 b. 0.05513 C. 7.402 (?) 3. An ornament is said to be of solid gold. It displaces 2.78 mL. of water and has a mass of 50.1 g. Calculate density and show whether the ornament be of solid gold or not? Gdensity of Gold- 19.3g/em3) (5 pts) The element lithium has two isotopes. Li-6 with a mass of 6.015 amu and natural abundance of 7.79% and Li-7 with a mass of 7.016 amu and natural abundance of 92.21%. Calculate the relative atomic mass of lithium. Report your answer to appropria sig. fig. (5 pts)

Explanation / Answer

3. Density = Mass / Volume of water displaced ( Volume of water displaced represents the actual volume of ornament)

Density = 50.1 g / 2.78 mL = 18.0215827 g / mL ( 1 mL = 1 cm 3-)

According, to the significant digit division/ Multiplication rule, the final answer obtained on division should have the same number of significant digits as in the lowest precise number( the number with lowest number of significant digits)

Now, since number of significant digits in 50.1 = 3 and 2.78 = 3

18.0215827 should be rounded off to three significant digits which gives 18.0 g/ cm3-.

Since the density obtained is different from that of theoratical gold, The ornament is not pure.

4) Relative atomic mass is given by : (Mass of isotope 1 * its relative abundance) + (Mass of isotope 2 * its relative abundance)

GIven, Mass of Li-6 = 6.015 amu , Abundance = 7.79% = 0.0779

Mass of Li-7 = 7.016 amu , Abundance = 92.21 % = 0.9221

Substituting,

Relative atomic mass = (6.015 amu * 0.0779) + (7.016 amu * 0.9221) = ( 0.4685685 amu) + (6.4694536 amu)

Applying Rule of mutiplication to first term ,No. of significant figure in 6.015 = 4 and 0.0779 = 3

So, final answer should have three significant figures i.e. 0.469

Similarly for second term, No. of significant digits in 7.016 =4 and 0.9221 =4

So, final answer should have four significant figures i.e.6.469

Significant rule of addition says that final answer should have number of decimal points as in the number with lowest decimal point

No. of decimal points in 0.469 = 3 and 6.469 = 3

So, final answer should have three decimal points i.e. 0.469 amu + 6.469 amu = 6.938 amu

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