# Questions

Title | Body |
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How do I find the initial energy of an electron given the wavelength and the final energy | An electron jumps to the n = 4 level of a hydrogen atom after absorbing a photon of wavelength 1875 nm. What energy level did the electron move from? I haven't found equations for how to to find the energy absourbtion, just emission. |

What is the percentage of cocaine in the mixture? | A sample of cocaine, C17H21O4N, is diluted with sugar, C12H22O11. When a 1.00 mg sample of this mixture is burned, 2.00 mg CO2 is formed. What is the percentage in this mixture? |

Why are they dividing by 2 to find average? | Why are the dividing by 2 for the average rate? They should divide only when comparing, right? Where am I going wrong? |

Can someone please explain and show me how to di this question please.... | Jacy bought a gold necklace weighing 21.3 grams from the flea market. She filled a graduated cylinder with water to the 5.0mL mark and dropped her necklace in. The level in the graduated cylinder rose to 704mL. is her necklace real or fake? |

chem question | could you please help me with this question: how many grams of water must be added to 200 ml of NaOH solution in order to have a solution with a specific gravity of 1.157, 13.55%? (Specific gravity= 1.32, 28.83%). |

How to convert wt% MgCO3 to mole% MgCO3 | I have geochemistry data for limestone samples consists of oxides and REE. I want to find out the mole% MgCO3 for the samples. I understand that I can use conversion factor of 3.4683 to convert MgO wt% to MgCO3 wt%. But from there I don't know how to proceed. |

Is this the correct oxidation numbers for H and O in hydrogen peroxide H2O2; H 1+, O 1- . Why or why not ? | Yes H is +1 and O is -1 is peroxides so these oxidation numbers are correct . |

What is the oxidation number of nitrogen in nitric acid,HNO3 ? | Nitrogen has +5 oxidation number in HNO3 |

Is the reaction 2Al(s) + 3Cl 2 (g) ----> 2AlCl 3 (s) can be considered as the redox reaction ? | Yes, since Al is underging an oxidation and Cl is undergoing reduction . |

Does a reducing agent oxidized or reduced in a oxidation-reduction reaction ? | A reducing agent oxidizes during a oxidation -reduction reaction |