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Starting from a 1 M stock of NaCl, how will you make 50 ml of 0.15 M NaCl?

WARRIOR [948]

Answer:

We need 7.5 mL of the 1M stock of NaCl

Explanation:

Data given:

Stock = 1M this means 1 mol/ L

A 0.15 M solution of 50 mL has 0.0075 moles NaCl per 50 mL

Step 2: Calculate the volume of stock we need

The moles of solute will be constant

and n = M*V

M1*V1 = M2*V2

⇒ with M1 = the initial molair concentration = 1M

⇒ with V1 = the volume we need of the stock

⇒ with V2 = the volume we want to make of the new solution = 50 mL = 0.05 L

⇒ with M2 = the concentration of the new solution = 0.15 M

1*V1 = 0.15*(50)

V1 = 7.5 mL

Since 0.0075 L of 1M solution contains 0.0075 moles

50 mL solution will contain also 0.0075 moles but will have a molair concentration of 0.0075 moles / 0.05 L =0.15 M

We need 7.5 mL of the 1M stock of NaCl

6 0

2 years ago

3. Dorji was provided with four colourless solutions. He was asked to

givi [52]

Answer:

First, we can test Solution 1. We know that Sodium Hydroxide is a strong base. If we test acids on blue litmus paper, they will turn red. If we test bases on red litmus paper, they will turn blue. So, you can test all the of the solutions- water, sodium hydroxide and hydrochloric acid with blue and red litmus paper. HCl, Hydrochloric acid is an acid, so it will turn blue litmus paper red. It will not turn red litmus blue. The acids will turn blue litmus paper red. The bases will turn red litmus paper blue. Only water is a neutral liquid, which will not turn blue litmus paper red or red litmus paper blue. It will not change the colour of it. Thus, if you test all the solutions with blue and red litmus paper, you will know which solution is water. Water is the only one which is neutral. It is the only solution which cannot change the colour of any litmus paper. Thus, you can identify it very easily.

5 0

3 years ago

Next to each formula, write the number of atoms of each element found in one unit of the compound

satela [25.4K]

To answer this question I would have to know the elements in the compound

7 0

3 years ago

The boiling point of water is 100ºC. The boiling point of acetone is 56ºC. Which statement about distilling a mixture of acetone

Anika [276]

Answer:

I think Acetone will be captured and cooled.

Explanation:

Distillation is a method of separation based on the difference in boiling point of two liquids.

The liquid that has a lower boiling point is first separated from the mixture. It vaporizes, cooled and collected before the liquid that has a higher boiling point.

In this case, acetone is captured and cooled before water since it has a boiling point of 56ºC and water has a boiling point of 100ºC.

3 0

1 year ago

Dissolving brass requires an oxidizing acid such as concentrated nitric acid. Nitrogen dioxide is produced as a byproduct in thi

polet [3.4K]

Answer:

Cu + 4 HNO₃ → Cu(NO₃)₂ + 2 NO₂ + 2 H₂O

Explanation:

Step 1: Write down the chemical formulas of given substances,

Copper Metal = Cu

Nitric Acid = HNO₃

Copper (II) Nitrate = Cu(NO₃)₂

Nitrogen Dioxide = NO₂

Water = H₂O

Step 2: Write down the unbalance Chemical equation,

Cu + HNO₃ → Cu(NO₃)₂ + NO₂ + H₂O

Step 3: Balance Cu atoms on both sides;

The number of Cu atoms on both sides are same. Hence, there number will remain the same.

Step 4: Balance N atoms on both sides;

As there is 1 N atom on left hand side and 3 N atoms on right hand side, so we will multiply HNO₃ by 3 to balance N on both sides, hence,

Cu + 3 HNO₃ → Cu(NO₃)₂ + NO₂ + H₂O

Step 5: Balance O atoms on both sides;

As there are 9 O atom on left hand side and 9 O atoms on right hand side, so they are balance.

Step 6: Balance H atoms on both sides;

As there are 3 H atom on left hand side and 2 H atoms on right hand side, so we will multiply H₂O by 2 as,

Cu + 3 HNO₃ → Cu(NO₃)₂ + NO₂ + 2 H₂O

By doing so the number of O atoms got imbalanced, so to balance O atoms again we will multiply HNO₃ by 4 as,

Cu + 4 HNO₃ → Cu(NO₃)₂ + NO₂ + 2 H₂O

Now, The Cu and H atoms are balanced, and the O atoms are greater on left hand side and the N atoms are greater on right hand side, therefore we will multiply NO₂ by 2 to balance both N and O as,

Cu + 4 HNO₃ → Cu(NO₃)₂ + 2 NO₂ + 2 H₂O

7 0

3 years ago