1) When 5.00g of copper reacts with oxygen, the copper oxide product has a mass

Question

1) When 5.00g of copper reacts with oxygen, the copper oxide product has a mass of 5.62g. What is the empirical formula of this copper oxide? MM Cu= 63.5, O= 16.0

2) What is the molarity of acetic acid, CH3COOH (MM= 60.0) in vinegar if a 5.00mL sample of vinegar requires 22.50mL of a 0.195M NaOH solution to neutralize it?

3) A 20.00mL sample of NaCl solution has a mass of 20.75g. After the NaCl solution is evaporated to dryness the dry salt has a mass of 4.35g. Calculate the following concentration for the NaCl solution, MM NaCl= 58.5

(a) % m/m (or % w/w)

(b) % m/v

(c) Molarity (M)

Explanation / Answer

1)moles of copper=5/63.5

=0.0787

moles of O=0.62/16

=0.03875

so the formula is CuO2

2)let the molarity be m.so,

CH3COOH + NaOh ---> CH3COONa + H2O

so m*5=22.5*0.195

or m=0.8775 M

3)a)%w/w = 4.35*100/(20.75)

=20.96 %

b)%m/v =4.35*100/20

=21.75 %

c)molarity=(4.35/58.5)*1000/20

=3.72 M

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