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A solution of NaOH has a concentration of 25.00% by mass. What mass of NaOH is present in 0.250 g of this solution? Use the periodic table in the toolbar if needed.

Answers

Answer 1

Answer:

Answer : The mass of NaOH present in the solution is, 0.0625 grams

Explanation : Given,

Mass % = 25 %

Mass of solution = 0.250 g

Formula used :

$Mass\%=\frac{\text{Mass of}NaOH}{\text{Mass of solution}}* 100$

Now put all the given values in this formula, we get the mass of NaOH.

$25=\frac{\text{Mass of}NaOH}{0.250g}* 100$

$\text{Mass of}NaOH=0.0625g$

Therefore, the mass of NaOH present in the solution is, 0.0625 grams

Answer 2

Answer: The concentration of NaOH is 25.00% by mass, it means that 25.00% of the mass of the solution is of NaOH. Hence:

$m_(NaOH)=25.00\%* m_(solution)\Longrightarrow m_(NaOH)=(25)/(100)* 0.250~g\iff\n\n\boxed{m_(NaOH)=0.0625~g}$

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Two chemicals A and B are combined to form a chemical C. The rate, or velocity, of the reaction is proportional to the product of the instantaneous amounts of A and B not converted to chemical C. Initially, there are 100 grams of A and 50 grams of B, and for each gram of B, 2 grams of A is used. It is observed that 15 grams of C is formed in 7 minutes. How much is formed in 28 minutes

Answers

Answer: 60 grams.

Explanation:

Given data:

Chemical A = 100 grams

Chemical B = 50 grams

For each gram of B 2 grams of A is used = 1:2.

15 grams of C is formed in 7minutes.

Solution

How many grams would be formed in 28mins?

= 15grams / 7 minutes

= 2.1423 grams/minute

If 2.1423 grams is formed/minutes

= 28minutes x 2.1423grams

= 60grams

60 grams of solution C would be formed in 28 minutes.

A 15.0 g piece of copper wire is heated, and the temperature of the wire changes from 12.0oC to 79.0oC. The amount of heat absorbed is 775 cal. What is the specific heat of copper?

Answers

Answer:

The specific heat of the copper is 0.771 cal/ grams °C

Explanation:

Step 1: Data given

Mass of the piece of copper = 15.0 grams

The temperature of the wire changes from 12.0 °C to 79.0 °C

The amount of heat absorbed is 775 cal

Step 2: Calculate the specific heat of copper

Q = m*c*ΔT

⇒with Q = the heat absorbed = 775 cal

⇒with m = the mass of the copper = 15.0 grams

⇒with c = the specific heat of copper = TO BE DETERMINED

⇒with ΔT = The change in temperature = 79.0 °C - 12.0 °C = 67.0 °C

775 cal = 15.0 grams * c * 67.0 °C

c = 0.771 cal/gm °C

The specific heat of the copper is 0.771 cal/ grams °C

a length of #8 copper wire (radius = 1.63 mm) has a mass of 24.0 kg and a resistance of 2.061 ohm per km. what is the overall resistance of the wire

Answers

m = pVol

p : copper density

Vol: volume

Vol = Al

A: area

L: length

m = p * A * L

L = m/p*A

To find the total resistance

Rtotal = R per Km * L/1000

Actually I think the question is missing the copper density.

Theoretical yield
2.05 g salicylic acid x (180g aspirin/1 mol) x (1 mol/138 g salicylic acid)

Answers

The question is incomplete; part of the data required in the question are shown:

Theoretical Yield: 2.05 g salicylic acid x (180g aspirin/1 mol) x (1 mol/138 g salicylic acid) 2. Mass of filter paper 2.56 g 3. Mass of filter paper and aspirin 5.42 g 4. Mass of aspirin (3-2) g. Percent Yield [(4)/(1)] x 100

Answer:

107%

Explanation:

We can calculate the theoretical yield as shown;

2.05g salicylic acid × 180g aspirin/1mol × 1 mol/138g of salicylic acid

Theoretical yield= 2.67 g of aspirin

Actual yield of aspirin is obtained from the experimental data;

Mass aspirin + filter paper= 5.42 g

Mass of filter paper= 2.56 g

Mass of aspirin= 5.42 g -2.56 g = 2.86 g

Hence actual yield of aspirin = 2.86 g

Percentage yield = actual yield/theoretical yield × 100

Percentage yield = 2.86/2.67 ×100 = 107%

1. (a) What name is given to the law describing the relationship between volume and pressure at constant temperature? Write a mathematical expression that describes this relationship. (2 marks)(b) Sketch a graph of the relationship described in part (a).