Concentrations of Solutions

[mandy]

I'm having some trouble understanding what they want me to do in this question :S

What is the mass of the solute in each of the following solutions?
a. 200mL of 1.5M sodium hydroxide solution (NaOH)
b. 50mL of 0.99M potassium carbonate (K₂CO₃)
c. 100mL of 1.20M ammonia (NH₃)

Some guidance please

[TrueTears]

b)

[mandy]

Thanks guys

[mandy]

Hey, I've got another question.

A 1.5L bottle of soft-drink contains 0.075g of calcium, present as calcium ions. What is the concentration of calcium in mg L^-1?

[TrueTears]

1.5 L : 0.075 g

1 L : 0.05 g

1 L : 50 mg

so

[mandy]

Thaaanks.

[mandy]

Calculate the molar concentration of the following solutions.

b. 100mL solution containing 3.0 X 10²⁰ ammonia molecules (NH₃)

c. 200mL water is added to 40mL of 0.25M KCl


How would I do either of these questions ?

[hyperblade01]

1. Use n = N/Na (Avogadra's number) to find mole

then c = n/v



2. Find the initial mole with n = cv

Now add .2 (remember volume is in litres) to get new v, then recalculate with c = n/v

[chem-nerd]

2. or just use c1v1 = c2v2

[hyperblade01]

2. or just use c1v1 = c2v2

Totally forgot about the dilution formula

[chem-nerd]

^^
think you've got yourself confused, it asks for concentration in mg L^-1

which is just mass (in mg) divided by volume (in L)

thus 0.075/1.5

(which is what TT did but with ratios)

[mandy]

Yeah, thanks though (:


Calculate the final molar concentrations when the following are mixed.

100mL of 0.50M NaOH and 20mL of 0.14M NaOH.

Should I be using some sort of ratio?

[vexx]

^^
think you've got yourself confused, it asks for concentration in mg L^-1

which is just mass (in mg) divided by volume (in L)

thus 0.075/1.5

(which is what TT did but with ratios)

Oh sorry! I thought it said find Mol mL-1 my bad! Ignore what i said (deleted)haha