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Bond [772]
3 years ago
15

Pre-lab Assignment

Chemistry
1 answer:
alina1380 [7]3 years ago
3 0

Answer:

1. d. Person A rounded their measurement

2) a. 105.

b. 76.4

c. 0.04

d. 1.988

Explanation:

1. Measuring an object is done with the least precise one. Person A recorded 1.5cm while Person B recorded 1.50cm of the same object. This measurement differs in the sense that Person A rounded up their measurement to 2 significant figures (1.5) while Person B recorded their answer as three significant figures (1.50).

2. During multiplication and division, the result is written as the measurement in the lowest significant figure.

a. 7.00 x 15.00 = 105. Calculator showed 105.00, which is 5 s.f (two zeros after decimal point are significant). The least significant figure is 3, hence 105.00 is rounded up to 105.

b. 40.2.1.901 = 76.4; The calculator answer of this operation is 76.420200 but since the lowest significant figure is 3. We round up our answer to 3 s.f i.e. 76.4

c. (0.003)(13.2) = 0.04. For this operation, calculator answer is 0.0396, however, the lowest significant figure in the question is 1 i.e. 0.003. Note that the two zeros before 3 are insignificant. Hence, our answer will be rounded up to 1 s.f i.e. 0.04

d. 1.590+ 0.3975 = 1.988. the calculator answer to this operation is 1.9875. However, the least significant figure in the question is 4 i.e. 1.590. hence, the answer will be rounded up to 4 s.f which is 1.988.

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A solution contains 35 grams of KNO3 dissolved in 100 grams of water at 40°C. How much more KNO3 would have to be added to make
Marta_Voda [28]

Answer:

32g

Explanation:

potassium nitrate has solubility of about 67g per 100g of water at 40°C, which means that potassium nitrate solution will contain 67g of dissolved salt for every 100g of water.

since at this temperature, our solution contains  35g of potassium nitrate 100g  of water. The solution will be unsaturated because of the less potassium nitrate.

to make saturated solution,

mass of potassuim nitrate = 67g - 35g

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which means dissolving another  32g  of potassium nitrate in solution at 40 °C will make saturated solution.

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<h3>Answer:</h3>

498 kj/mol

<h3>Explanation:</h3>
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In our case;

In 1 mole of the Oxygen molecule, there is one O=O bond

Energy absorbed to break O=O is 498 kJ/mol

Therefore, the ΔH required to break all the bonds in one mole of Oxygen(O₂) molecules is 498kJ/mol.

Note that, bond breaking is endothermic since energy is absorbed  from the surroundings.

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A quantitative observation is not necessarily more useful than a non-quantitative one. However, quantitative observations do allow one to find trends.

(a), the sun rising is a non-quantitative observation.

(b), knowledge of the numerical relationship between the weight on the Moon and on Earth, is a quantitative observation.

(c), watching ice float on water does not involve a measurement; therefore, it must be a qualitative observation.

(d) the fact that we know that the water pump won’t work for depths more than 34 feet makes it quantitative. Again, seeing numbers is a giveaway that it’s a quantitative <span>observation. Quantitative is where you deal with numbers.</span>
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19~ \text{kcal} = 19 \times 1000 ~\text{cal } = 19000~ \text{cal} = 19000 \times 4.184~ \text{J} = 79496~ \text{J}

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