1. gold (au) has been used to make ornamental objects and jewelry for thousand of years. gold nuggets found in a stream are ve9aury easy to work and were probably one of the first metal used by humans (1 mol of gold (au)= 196.97g)cal culate the:
A. number of moles in a 95.0 g sample of a gold nugget.
b. number of atoms in a 95.0 g sample of gold nugget
2. during exercise, llactic acid (C3 h6 o3) forms in the muscle causing cramp if 5.0 g of lactic acid (c3h6o3) concentrate in you leg muscle how many moleclues of lactic acid is causing your pain (C=12.0 g /mol,H =1.008 g/mol,0=16.0g/mol

\text{number of Au atoms = 95.0 g Au} × \frac{\text{1 mol Au}}{\text{196.97 g Au}} × \frac{\text{6.022 × 10²³ Au atoms}}{\text{1 mol Au}}number of Au atoms = 95.0 g Au×

196.97 g Au

1 mol Au

×

1 mol Au

6.022 × 10²³ Au atoms

\boxed{\text{number of Au atoms = 2.90 × 10²³ atoms}}

number of Au atoms = 2.90 × 10²³ atoms

2.A mole is a unit of many particles (atoms, molecules, ions) where 1 mole is the number of particles contained in a substance that is the same amount as many atoms in 12 gr C-12

1 mole = 6.02.10²³ particles

While the number of moles can also be obtained by dividing the mass (in grams) with the molar mass of element or molecule

So looking for moles we can search in 2 ways

1 . Avogadro's number

n = N : No

N = number of gas particles

No = Avogadro number (6.02.10²³)

n = number of moles

2. Molar mass

n = mass : molar mass

m = mass

M = relative molecular mass

Given

5.0 g of Lactic acid (C₃H₆O₃)

Required

Moles of Lactic acid

Solution

Molar mass of Lactic acid :

= 3 x 12 + 6 x 1 + 3 x 16

= 90 g/mol

\tt mol=n=\dfrac{5.0~g}{90~g/mol}=\boxed{\bold{0.056}}mol=n=

90 g/mol

5.0 g

=

0.056

Learn more

the mole fractions of the solute and the solvent