Crosswords0 min ago
Help Me With These Calculations Please!!!!
3 Answers
I have to do alot of calculations and most of them are on same pattern but I dont know how to solve them.. Please if anyone help me understand that. for example,
1). What weight of potassium permanganate is required to prepare 250ml of a solution such that 10 mL diluted to 1 litre will give a 1 in 10,000 solution?
A 2.5g
B 10 g
C 25 g
D 100 g
E 250 g
2). To prepare 5 litres of a solution containing potassium ions 1 mmol/mL. What weight of potassium chloride is required?
(atomic weight of potassium = 39: atomic weight of chlorine = 35.5)
A 0.3725 g
B 0.745 g
C 37.25 g
D 74.5 g
E 372.5 g
1). What weight of potassium permanganate is required to prepare 250ml of a solution such that 10 mL diluted to 1 litre will give a 1 in 10,000 solution?
A 2.5g
B 10 g
C 25 g
D 100 g
E 250 g
2). To prepare 5 litres of a solution containing potassium ions 1 mmol/mL. What weight of potassium chloride is required?
(atomic weight of potassium = 39: atomic weight of chlorine = 35.5)
A 0.3725 g
B 0.745 g
C 37.25 g
D 74.5 g
E 372.5 g
Answers
1) We have to work backwards to calculate the weight. a 1 in 10,000 solution contains 1g in 10 litres which is the same as 0.1g in 1 litre. 10 ml containing 0.1g is diluted to 1 litre to make the required final solution. 250ml of this solution contains 250/10 x 0.1g = 2.5g Answer A I hope that's right and makes sense - my brain hurts now!!
19:21 Wed 15th Jan 2014
1) We have to work backwards to calculate the weight.
a 1 in 10,000 solution contains 1g in 10 litres which is the same as 0.1g in 1 litre.
10 ml containing 0.1g is diluted to 1 litre to make the required final solution.
250ml of this solution contains 250/10 x 0.1g = 2.5g
Answer A
I hope that's right and makes sense - my brain hurts now!!
a 1 in 10,000 solution contains 1g in 10 litres which is the same as 0.1g in 1 litre.
10 ml containing 0.1g is diluted to 1 litre to make the required final solution.
250ml of this solution contains 250/10 x 0.1g = 2.5g
Answer A
I hope that's right and makes sense - my brain hurts now!!