Considering the reaction of hydrogen and oxygen to produce water. If 24.6 g of water is produced and 2.9 g of hydrogen is used, the amount of oxygen needed is 21.87 grams
The best way to solve this question is to write out the reaction between hydrogen and oxygen that resulted in the formation of water.
So, we have:

From the above reaction;
2 moles of hydrogen gas reacted with 1 mole of oxygen to produce 2 moles of water.
If;
- 1 mole of O₂ = 32 grams of O₂
- 2 mole of H₂O = 2 × 18 grams of H₂O
- 2 mole of H₂O = 36 grams of H₂O
We can deduce that since 1 mole of O₂ produced 2 moles of H₂O;
Thus, 32 grams of O₂ is needed to produce 36 grams of H₂O.
∴
To produce, 24.6 grams of H₂O, we have:

= 21.87 grams of oxygen.
Therefore, we can conclude that the amount of oxygen needed is 21.87 grams.
Learn more about chemical reactions here:
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The amount of joules of heat that are lost when 150.0 g of steam are cooled from 124 °c to 86 °c is = -11343 joules
calculation
heat(Q) = mass(m) x specific heat capacity(C) x change in temperature (ΔT)
where,
Q=? joules
M=150.0 g
C for steam = 1.99 j/g/°c
ΔT= 86°c-124°c = -38°c
Q is therefore = 150.0 g x 1.99 j/g/°c x -38°c =-11343 joules
That’s a dumb question, because It depends on the experiment. I would guess “a” or “d” because in most cases running out of time during a lab, or getting impatient, etc can give you a lower yield.
Unless I’m misreading “d”, it just seems like a more in-depth version of “a”. So it wouldn’t hurt to try that one.
Answer: I'm not sure what answer to give you since there are no answer choices, but here is what I got.
Explanation:
Mg is a reducing agent, Fe 2O 3 is an oxidizing agent.
Igniting a mixture of Fe2O3 and Al with a magnesium ribbon fuse produces molten iron and aluminum oxide in an impressive exothermic reaction.
Hope this helped a little:(
The nucleus is where the protons and neutrons are found. the mostly space electron cloud is where the electrons are found, surrounding the nucleus.