**1. Calculate gram equivalents of the following – (Given – Eq.wt of O=8,Al =9)i)7 × 10 ^{-3} kg of oxygen.ii) 4.5 × 10^{-3} kg of aluminium**

**A:** Formula used – Gram equivalent =w/EW.

Note that the weight of the elements are given in kg. So, we need to first convert them to grams.

*1kg = 1000g i.e 10 ^{3} gSo, 1g = 10^{-3} kg*

I)Thus, 7 × 10^{-3} kg = 7g of oxygen.

Gram equivalent = weight of the element /equivalent weight of the element(EW)

∴ Gram equivalent of oxygen – 7/8 = 0.875.

ii) Similarly, gram equivalent of aluminium = 4.5/9 = 0.5.

**2.Calculate the equivalent weight of C _{6}H_{5}COOH.**

**A:** Molecular weight of C_{6}H_{5}COOH = 6(12)+5(1)+12+2(16)+1 = 122g .

This compound has only one replaceable hydrogen. So, n-factor =1.

Equivalent weight = Molecular weight /nf = 122 /1 = 122.

**3.What is the molarity of 0.3181 N HCl?**

**A: **We know that , Normality = molarity /n_{f}.

∴Molarity = n_{f} × normality.For HCL the n-factor is 1.

∴ The molarity of this acid is equal to its normality i.e 0.3181.

**4.A solution has a concentration of 0.5 mg mL ^{-1}.What is its concentration in ppm?**

**A:** ppm means mg of solute per litre of solution.The quantity given is per mL of solution.So, we have to convert ml into litres.

1000ml = 1litre

∴1ml = 10^{-3} L

Thus, concentration in ppm = 0.5 ÷10^{-3} mg L^{-1} = 500ppm.

**5.A concentrated solution of aqueous ammonia is 28.0% w/w NH _{3} and has adensity of 0.899 g/mL. What is the molar concentration of NH_{3} in this solution?**

**A:** %w/w means gms of solute per 100 g of solution.This means the solution of ammonia has 28g of NH_{3} in 100g of solution.

We know density of the solution.

Density = ** mass of the solution**/volume.

∴Volume = mass/density = (

**)/(0.899 g/mL) = 111.2mL**

*100g*Volume of solution =111.2mL= 0.1112 L.

Thus, 28g of NH_{3} is present in 0.11L of solution.So, in 1 liter we will have 28/0.11 = 254.5g of NH_{3}.

no.of moles of solute = weight in 1 litre of solution/M.wt = 254.5/17=14.97 g/mole.

Thus, the molar concentration of this solution is 14.97g/mol.

We will discuss some other fundamental concepts of analytical chemistry in the next post. Till then ,

Be a perpetual student of life and keep learning…

Good day !

References and further reading –

1.http://spots.gru.edu/cklug/CHEM2810Fall2015%5CSolutions-Normality.html

2.https://www.ausetute.com.au/partspm.html