Skip to content

Help Zone

Chemistry

69

Questions

71

Explanations

Default Avatar
What is your question?

{t c="richEditor.description.title"} {t c="richEditor.description.paragraphMenu"} {t c="richEditor.description.inlineMenu"} {t c="richEditor.description.embed"}

Formulate your question as clearly as possible.

Do not publish anything offensive.

Make sure that your question hasn’t already been asked.

Discussion List

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 10mo.

    I need to explain why when we look at a laser ray, we can't see its trajectory, but when chalk powder floats in the air in front of it, we can suddenly see the ray. Can anyone help me? Thank you! 

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    At 25 degrees Celcius, the volume of a gas is 4,6L at a pressure of 98 kPa. What will be its volume if we triple its pressure without changing its temperature? 

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    How can I go from Celcius to Kelvin?

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    Hello!

    The density of a gas can vary, but why?

    thank you!

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    Hello, I don’t understand why salt melts ice. Could you explain it to me using the atomic model please?

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    True or false - Only endothermic reactions absorb energy.

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    Hi,

    Why are we increasing the amount of carbon dioxide in greenhouses?

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    Hello, 

    I have the following equation at equilibrium : 

    HF = H+ + F-   Kc = 6,7 x 10^-4

    How do I know if the direct or the indirect reaction is favored?

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    What is the meaning of a negative temperature when using the calorimetry formula (Q=mc△t)?

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    Good morning,

    What is the difference between an elastic and an unelastic collision?

    Thank you

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    Hi Alloprof, 

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

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary V • 11mo.

    Hello,

    What is the normal atmospheric pressure?

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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!

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    What is the periodicity of properties?

  • Verified by Alloprof
    NaiveAbafar3712avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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)

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

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

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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.

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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!

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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?

    Thank you for your help!!

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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

  • Verified by Alloprof
    FairTangerine2097avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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!

  • Verified by Alloprof
    FairTangerine2097avatar
    Verified by Alloprof
    Secondary IV • 11mo.

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

  • Verified by Alloprof
    FairTangerine2097avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    Hello, I do not understand the principle of a titration

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

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

  • Verified by Alloprof
    SkillfulGrasshopper3789avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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?

    Thanks in advance :)

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    Hello,

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

    Thank you so much!

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    Hello!

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

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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 :))

  • Verified by Alloprof
    TomateSupra7536avatar
    Verified by Alloprof
    Secondary IV • 11mo.

    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 !!!


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

  • Verified by Alloprof
    SkillfulGrasshopper3789avatar
    Verified by Alloprof
    Secondary V • 11mo.

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