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Alex17521 [72]
3 years ago
9

The 4-4-9 system is used to estimate the number of _______ in food. Question 9 options: A) kilojoules B) calories C) joules D) n

utritional Calories
Chemistry
1 answer:
eimsori [14]3 years ago
6 0

Answer: B) calories

Explanation:

The 4-4-9 system is used to estimate the number of calories in food. Under this system, it is assumed that one gram of Protein, one gram of Carbohydrates and one gram of Fats each contribute 4, 4 and 9 calories respectively to the caloric total.

This means that to find out the number of calories in food, multiply the total grams of proteins by 4, the total grams of carbohydrates by 4 and the total grams of Fats by 9 and then add up the results to find out the caloric contribution of Protein, Carbohydrates and Fats.  

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Answer:

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Explanation:

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4 years ago
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A sample of 9.27 g9.27 g of solid calcium hydroxide is added to 38.5 mL38.5 mL of 0.500 M0.500 M aqueous hydrochloric acid. Writ
navik [9.2K]

<u>Answer:</u> The excess reagent for the given chemical reaction is calcium hydroxide and the amount left after the completion of reaction is 0.115375 moles. The amount of calcium chloride formed in the reaction is 1.068 grams.  

<u>Explanation:</u>

  • To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}   ....(1)

<u>For calcium hydroxide:</u>

Given mass of calcium hydroxide = 9.27 g

Molar mass of calcium hydroxide = 74.093 g/mol

Putting values in above equation, we get:

\text{Moles of calcium hydroxide}=\frac{9.27g}{74.093g/mol}=0.125mol

  • To calculate the moles of a solute, we use the equation:

\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}

We are given:

Volume of hydrochloric acid = 38.5mL = 0.0385 L   (Conversion factor: 1 L = 1000 mL)

Molarity of the solution = 0.500 moles/ L

Putting values in above equation, we get:

0.500mol/L=\frac{\text{Moles of hydrochloric acid}}{0.0385L}\\\\\text{Moles of hydrochloric acid}=0.01925mol

  • For the given chemical equation:

2HCl(aq.)+Ca(OH)_2(s)\rightarrow CaCl_2(s)+2H_2O(l)

Here, the solid salt is calcium chloride.

By Stoichiometry of the reaction:

2 moles of hydrochloric acid reacts with 1 mole of calcium hydroxide.

So, 0.01925 moles of hydrochloric acid will react with = \frac{1}{2}\times 0.01925=0.009625moles of calcium hydroxide.

As, given amount of calcium hydroxide is more than the required amount. So, it is considered as an excess reagent.

Thus, hydrochloric acid is considered as a limiting reagent because it limits the formation of product.

  • Amount of excess reagent (calcium hydroxide) left = 0.125 - 0.01925 = 0.115375 moles

By Stoichiometry of the reaction:

2 moles of hydrochloric acid produces 1 mole of calcium chloride.

So, 0.01925 moles of hydrochloric acid will produce = \frac{1}{2}\times 0.01925=0.009625moles of calcium chloride.

Now, calculating the mass of calcium chloride from equation 1, we get:

Molar mass of calcium chloride = 110.98 g/mol

Moles of calcium chloride = 0.009625 moles

Putting values in equation 1, we get:

0.009625mol=\frac{\text{Mass of calcium chloride}}{110.98g/mol}\\\\\text{Mass of calcium chloride}=1.068g

Hence, the excess reagent for the given chemical reaction is calcium hydroxide and the amount left after the completion of reaction is 0.115375 moles. The amount of calcium chloride formed in the reaction is 1.068 grams.

5 0
3 years ago
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The oh concentration in a 1.0 x10 3 m ba oh 2 solution is
Lisa [10]
Ba(OH)2 dissociates according to the equation below to yield Barium ions and hydroxide ions.
Ba(OH)2 = Ba²⁺ + 2 OH⁻
The concentration of Ba²⁺ is 1.0 ×10^-3 M
Thus that of OH⁻ ions will be 2× 1.0 ×10^-3 = 2.0 × 10^-3 M
Thus; the answer is 2.0 × 10^-3 M
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3 years ago
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Answer:

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We are asked to solve for the arc length of the intercepted arc and the formula is shown below:
Arc length = 2*pi*r(central angle/360°)
r = 5 feet
central angle = 10°

Solving for the arc length, we have:
Arc length = 2*3.14*5 (10/360)
Arc length = 0.872 feet

The arc length is 0.872 feet.
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