Chemistry Concentration and Molarity Quiz

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Questions and Answers

What is the percentage strength of a solution that is 1 part per million?

0.1%

0.01%

0.0001% (correct)

0.001%

How much of a drug is required to prepare 240 grams of a 5% w/w solution?

15 g

12 g (correct)

10 g

14 g

What is the percentage of iodine in a tincture with 3 g of iodine in 150 mL?

2% (correct)

What is the percentage of ethanol in a solution that contains 20 mL of ethanol in 40 mL?

50% v/v Signup and view all the answers

What is the percentage weight in volume (w/v) of a solution containing 25 g of dextrose in 500 mL?

5% w/v Signup and view all the answers

What is the percentage w/v of magnesium carbonate in a syrup containing 10 g of magnesium carbonate in a total volume of 1000 mL?

1% w/v Signup and view all the answers

How much drug is contained in 5 mL of cough syrup if 100 mL contains 200 mg of the drug?

10 mg Signup and view all the answers

What is the total weight of the ingredients in an ointment composed of 14 g liquid paraffin, 38 g soft paraffin, and 12 g hard paraffin?

64 g Signup and view all the answers

What is the percentage of soft paraffin in 100 g of ointment?

59.38% Signup and view all the answers

How many milligrams of sodium hydroxide (NaOH) are required to achieve a concentration of 10 mmol in 1 L of water?

400 mg Signup and view all the answers

What is the molecular weight of potassium hydroxide (KOH)?

56 g Signup and view all the answers

In how many kilograms is 111 mg of calcium chloride (CaCl₂) expressed when converted to grams?

0.00111 kg Signup and view all the answers

How many moles of NaCl are present in a 1 L solution containing 117 g of NaCl?

2 mol Signup and view all the answers

What is the formula for calculating the multiplying factor in extemporaneous dispensing?

Required Quantity / Formula Quantity Signup and view all the answers

What is the total weight percentage of the three components in the ointment?

100.00% Signup and view all the answers

What is the purpose of checking the total percentage of ointment ingredients?

To confirm the total is 100% Signup and view all the answers

What is the total amount of white soft paraffin needed for preparing 250 g of the ointment?

242.5 g Signup and view all the answers

In the preparation of Syrup BP, how is the concentration of sucrose expressed?

w/w Signup and view all the answers

What is the purpose of the dilution equation C₁V₁=C₂V₂?

To solve problems related to changing concentrations Signup and view all the answers

How is the concentration of formaldehyde specified in Formaldehyde Solution BP?

Weight per weight (w/w) Signup and view all the answers

When calculating quantities for a preparation, what remains unchanged regardless of the total amount prepared?

The percentage concentration of each ingredient Signup and view all the answers

If 120 mL of a 12% w/v solution is diluted to 240 mL, what is the formula to find the final concentration?

C₁V₁=C₂V₂ Signup and view all the answers

What quantity of salicylic acid is needed for preparing 250 g of the ointment?

2.5 g Signup and view all the answers

In which scenario is the weight/weight convention not applied?

In liquid ingredients expressed as a percentage Signup and view all the answers

What is the concentration of the diluted solution when 120 mL of a 12% solution is diluted to 240 mL?

6% Signup and view all the answers

When 200 mL of a 2.5% w/v solution is diluted to 750 mL, what is the final concentration in percentage?

0.67% Signup and view all the answers

How much volume of a 1% w/v solution can be prepared using 75 mL of a 5% w/v solution?

375 mL Signup and view all the answers

What percentage concentration of atropine is achieved when 150 mg of atropine powder is mixed with 50 g of lactose?

0.3% w/w Signup and view all the answers

In the alligation method, if the target concentration needed is 6% w/w, which concentrations can be used in the calculation?

2% w/w and 0.8% w/w Signup and view all the answers

If you need to make 100 mL of a 2% w/v suspension, which amount of the starting material should be used based on the alligation method?

20 mL Signup and view all the answers

What would be the total number of parts in the alligation method when mixing two components with concentrations of 2% and 0.8% to achieve 1%?

1.5 parts Signup and view all the answers

When using the dilution equation, what does the variable C₂ represent?

Final concentration Signup and view all the answers

What should you consult to verify the appropriateness of a drug dose?

A recognized reference book Signup and view all the answers

How is the dose for hypertension expressed in the BNF for verapamil?

240-480 mg daily in divided doses Signup and view all the answers

What is a reason for consulting the prescriber regarding the verapamil prescription?

The dose is higher than recommended Signup and view all the answers

Which formula is used to calculate an infant's dose based on age?

Fried's rule for infants Signup and view all the answers

What is the common method for calculating children's doses when weight is unavailable?

Fried's rule, Clark's rule, or BSA method Signup and view all the answers

What does the calculated dose using Clark's rule depend on?

Child's weight in kg Signup and view all the answers

Which of the following statements describes a key difference in dosing for hypertension compared to other indications for verapamil?

It requires daily dosing divided into multiple intakes Signup and view all the answers

What underlying concept is crucial when interpreting dosage recommendations from reference sources?

Familiarity with the terminology used Signup and view all the answers

Study Notes

Expressing Concentrations

1 part per million = 1: 1 000 000 = 1 × 10^-4%
Percentage weight in weight (w/w): the number of grams of an active ingredient in 100 grams of solid or liquid.
Percentage weight in volume (w/v): the number of grams of an active ingredient in 100 mL of liquid.
Percentage volume in volume (v/v): the number of millilitres of an active ingredient in 100mL of liquid.

Moles and Molarity

A 1 molar solution (1 mol) contains the molecular weight of a drug in grams in 1 litre of solution.
1 millimole (mmol) contains one-thousandth of a mole in 1 litre.

Calculating Quantities From A Master Formula

The multiplying factor equals the required quantity divided by the formula quantity.

Changing Concentrations

The dilution equation is used to calculate concentration changes: C₁V₁=C₂V₂
- C₁ and V₁ are the initial concentration and quantity.
- C₂ and V₂ are the final concentration and quantity.

Alligation

Alligation is a method for solving the number of parts of two or more components of known concentration to be mixed when the final desired concentration is known.

Checking Doses

Always consult a recognized reference book, like the British National Formulary (BNF), to check drug doses.
Be aware of terminology variations to avoid misinterpretations and potential errors.

Calculations of Children's Doses

When clinical studies are not available, the following formulas can be used to estimate children's doses:
- Fried's rule for infants: age (months) × adult dose / 150 = infant dose
- Clark's rule: weight (in kg) × adult dose / 75 = child dose
- Body surface area method (BSA): BSA of child (m²) × adult dose / 1.73 m² (average adult BSA) = approximate child's dose

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Description

Test your knowledge on expressing concentrations, understanding moles and molarity, as well as calculating quantities from formulas. This quiz covers the essential concepts needed for mastering solution preparation and concentration adjustments in chemistry.