QUESTION

Calculating the number of moles

THIS EXPOSES THE LEARNER TO THREE FOLD APPROACHES OF CALCULATING THE NUMBER OF MOLES, BY FORMULAE AND BY FIRST PRINCIPLES METHOD

SITUATION 1: CALCULATING MOLES FROM MASS.

SITUATION 2: CALCULATING MOLES FROM VOLUME AND MOLAR VOLUME.

SITUATION 3: CALCULATION MOLES FROM MOLARITY AND VOLUME.

(a)(i) What is a mole?

(ii) How do you calculate the number of moles?

(b)(i) Calculate the number of moles of 6g of calcium carbonate. ( Ca=40,C=12,O=16)

(ii) Given that the number of moles of sodium hydroxide are 0.05, find its mass.

(Na=23,O=16, H=1)

(iii) 2.5g of solid X has 0.05 moles. What is the Relative molecular mass (RMM) of X?

(iv) How many copper atoms are there in copper plate weighing 48g? (Cu = 64)?

(c)(i) Find the number of moles contained in 20cm3 of carbondioxide at S.T.P.

( 1 mole of gas at S.T.P occupies 22.4 dm3)

(ii) A gas Y occupying a vessel contains 0.0125 mole of the gas. What is the volume of Y in the vessel at R.T?( 1 mole of gas at R.T occupies 24dm3)

(d) (i) calculate the number of moles in 20cm3 of 0.2M sodium hydroxide solution.

(ii) 25cm3 of a solution of W contains 0.001335 moles. Calculate the molarity of W.

(iii)A 0.05M nitric acid solution contains 0.00145 moles. What is the volume of this solution?

(e) When a sample of calcium carbonate was heated to complete decomposition, 46cm3 of carbondioxide was produced at s.t.p. What was the mass of the calcium carbonate sample?

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