## Contest: It Pays to Use Alloprof This Summer!

Ask a school-related question in the Help Zone and you could win \$100 for a summer activity.

# Help Zone

## Discussion List

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Secondary V • 2yr.

Hi Alloprof,

Do gas particles still have kinetic energy below 0 degrees Celcius?

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Secondary V • 2yr.

Hello,

What is the normal atmospheric pressure?

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Secondary IV • 2yr.

I don't understand how to solve this problem:

The atomic mass of isotope # 1 of element Ab is 73 au. The atomic mass of isotope # 2 of the element Ab is 76 au. The atomic mass of isotope # 3 of the element Ab is 74 au. The relative frequencies of each isotope are 10%, 80% and 10%, respectively.

Find the average atomic mass.

Thank you!

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Secondary IV • 2yr.

What is the periodicity of properties?

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Secondary IV • 2yr.

Emilie suffers from diabetes. Therefore, after having lunch, traces of glucose (C6H12O6) can be found in her blood. What is the total mass of sugar that can be found in her blood before it reaches a concentration of 10 mmol / L? (hint: volume of blood = 5L)

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Secondary IV • 2yr.

How do you distinguish between metals, nonmetals and metalloids in the periodic table?

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Secondary IV • 2yr.

Hi!

I have an exercise that asks me to determine the mass of sodium hydroxide (NaOH) in a basic solution by titrating it with a 1.8 mol / L acidic solution. The titration shows a neutralization volume of 30 mL for the acid and an initial volume of 20 mL for the base. I am not sure how to find the mass.

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Secondary IV • 2yr.

Hi!

I'm not sure if I understand how a titration can help us to know the concentration of a solution ... Can someone explain it to me please?

Thank you very much in advance!

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Secondary IV • 2yr.

Hi! I'm not sure I understand how pH works.

Is the higher, the more acidic?

And if for example I have a solution with a pH of 4 and another with a pH of 8, is the second solution twice as acidic as the first?

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Secondary IV • 2yr.

I have a hard time understanding how why ° C is used in the thermal energy equation Q = m * c * delta T. In many chemistry exercises, we have to use Kelvin. Thank you

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Secondary IV • 2yr.

Hello,

I have a hard time understanding how an acid-base neutralization is done in a lab. Could you explain it to me please?

Thank you so much!

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Secondary IV • 2yr.

How do the different characteristics of the elements change in the periodic table?

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Secondary IV • 2yr.

Hello, I do not understand the principle of a titration

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Secondary IV • 2yr.

Hi, I don't understand half life ???

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Secondary IV • 2yr.

Hello! I'm not sure if the Q in Q = m * c * ∆T means the heat or thermal energy?

Also, when is the Q positive and negative?

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Secondary IV • 2yr.

Hello,

Could you explain to me what are the differences between the families of the periodic table please?

Thank you so much!

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Secondary IV • 2yr.

Hello!

Can 2 elements have the same atomic number? Thank you :)

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Secondary IV • 2yr.

Hello!

I was wondering, is there a particular order in the periodic table? Because from left to right and from top to bottom the number in the box starts from 1 and goes up, but does this number mean something or is it a reference number that has been set randomly? Thanks for your time :))

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Secondary IV • 2yr.

Hi!

I was reviewing and trying to remember how to find the number of protons, electrons and neutrons in an atom? (I will put an example below) Thank you !!!

$$_{92}^{235}U$$

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Secondary V • 2yr.

How do I answer this question: how many moles of oxygen are there in 2.25 g of CO2? Thank you!

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Secondary IV • 2yr.

Ok, I understand that in an acid-base neutralization, we mix an acid and a base in a solution, but I don't understand how the pH becomes neutral again after ...? Can you explain this to me please?

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Secondary IV • 2yr.

Hello again :)

Ok if I have a solution where I have to use colorimetric indicators, how do I use several at the same time to know the pH approximately? Do I simply combine them?

thank you

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Secondary IV • 2yr.

Hi!

If a solution is alkaline, is it acidic or basic? Thanksss

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Secondary IV • 2yr.

Hi again!

What does “ph is measured on a logarithmic scale” mean ????

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Secondary IV • 2yr.

hi!

Why can several pH indicators be used in an experiment? How can the appropriate one be determined? Thank you :))

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Secondary IV • 2yr.

Hello,

Could you explain to me what the molar mass is? I can't quite understand.

Thank you so much!

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Secondary IV • 2yr.

Helloo, what is the difference between a mole and the Avogadro number?

Thank you!

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Secondary IV • 2yr.

Hello,

I have trouble differentiating between exothermic and endothermic reactions according to their enthalpies. Do you have any tips or summaries?

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Secondary IV • 2yr.

Hello,

I am having difficulty understanding how the thermal energy formula works. Could you explain to me, please?

Thank you so much!