Question

1. A penny weighs about 3.0 g and you will be using roughly 1/4^th of a penny. Assuming that the entire penny sample is purely copper. How many moles of copper will you use sample? Report your answer with two significant figures and do not write the units

2. To be sure copper is the limiting reagent, you will use the other reagents in 20-times molar excess. Concentrated nitric acid is 15.8 mol/L. How many milliliters of concentrated nitric acid are needed to obtain 0.24 moles of nitric acid?

Report your result with two significant figures, do not write the units.

3. To be sure copper is the limiting reagent, this you will use the other reagents in excess. The sodium hydroxide solution available is 3.0 mol/L. How many milliliters of sodium hydroxide solution are needed to obtain 0.24 moles of sodium hydroxide?

Report your result with 2 significant figures and do not write the units.

4. To be sure copper is the limiting reagent, this you will use the other reagents in excess. The sulfuric acid solution available is 6.0 mol/L. How many milliliters of sulfuric acid solution are needed to obtain 0.24 moles of sulfuric acid ?

Report your result with 2 significant figures and do not write the units. PLEASE SHOW ALL WORKING FOR ALL QUESTIONS

Answer 1

1)

mass of Cu used = (1/4)*3.0 g

= 0.75 g

Molar mass of Cu = 63.55 g/mol

mass(Cu)= 0.75 g

use:

number of mol of Cu,

n = mass of Cu/molar mass of Cu

=(0.75 g)/(63.55 g/mol)

= 1.18*10^-2 mol

Answer: 1.2*10^-2 mol

2)

[HNO3] = 15.8 mol/L

number of moles = 0.24 moles

use:

number of moles = [HNO3]*volume

0.24 moles = 15.8 mol/L * volume

volume = 0.015 L

= 15 mL

Answer: 15 mL

3)

use:

number of moles = [NaOH]*volume

0.24 moles = 3.0 mol/L * volume

volume = 0.080 L

= 80. mL

Answer: 80. mL

4)

use:

number of moles = [H2SO4]*volume

0.24 moles = 6.0 mol/L * volume

volume = 0.040 L

= 40. mL

Answer: 40. mL