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The number of 20-g ice cubes required to absorb 47 kJ from a glass of water upon melting is 7 icecubes
Why?
We are going to clear from the equation of the released heat, the mass of ice (m). The specific latent heat of fusion of ice is 336 kJ/kg:
So, 7 ice cubes are required to absorb that amount of heat from the glass of water.
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Answer:
In this chemical reaction, which is considered irreversible, that is why the reaction arrow is ONE and unidirectional and not two in opposite directions, which means reversibility of the reaction.
In summary, if we look closely at the reaction, we observe that the stoichiometric values are balanced in the reaction, therefore there is THE SAME AMOUNT OF REAGENTS AS PRODUCTS.
This phenomenon has to be met in ALL CHEMICAL REACTIONS, the stoichiometric balance is essential for this reaction to be well expressed.
Why is stoichiometric balance so important? Why we indicate that we have the same amount of reagents as products, means that NOTHING IS LOST, EVERYTHING IS TRANSFORMED in the matter of the organic compounds that reacted.
Explanation:
Although if we observe the stoichiometric values well they are not correct with respect to oxygen, therefore it would be necessary to correct that in the chemical reaction, but above we briefly explain why the balancing of the reactions and the relationship they have with the conservation of the mass.
The law of conservation of mass indicates that mass is never lost, but is transformed, like energy, considering that it happens in terrestrial life.
Answer:
- <u><em>1.7 × 10³ kg of ore.</em></u>
Explanation:
Call X the amount of aluminum ore mined to produce 1.0 × 10³ kg the aluminum metal.
Then, taking into account the yield of the reaction (82 % = 0.82) and the percent of aluminun in the ore (71% = 0.71), you can write the following equation:
- X × 71% × 82% = 1.0 × 10³ kg
↑ ↑ ↑ ↑
(mass of ore) (% of Al in the ore) (yield) ( Al metal to obtain)
You must just simplify, solve and compute:
- X = 1,000 / (0.71 × 0.82) = 1,000 / 0.5822 = 1,717.6 Kg
Round to two significant figures; 1,700 kg = 1.7 × 10³ kg of ore ← answer.
Answer: The empirical formula of the compound is 
Explanation:
Empirical formula is defined formula which is simplest integer ratio of number of atoms of different elements present in the compound.
Percentage of iron in a compound = 36.76 %
Percentage of sulfur in a compound = 21.11 %
Percentage of oxygen in a compound = 42.13 %
Consider in 100 g of the compound:
Mass of iron in 100 g of compound = 36.76 g
Mass of iron in 100 g of compound = 21.11 g
Mass of iron in 100 g of compound = 42.13 g
Now calculate the number of moles each element:
Moles of iron=
Moles of sulfur=
Moles of oxygen=
Divide the moles of each element by the smallest number of moles to calculated the ratio of the elements to each other
For Iron element = 
For sulfur element =
For oxygen element = 
So, the empirical formula of the compound is
