When the oxidation number of an element decreases over the course of a reaction, that element has beenwhich of the following chemical reactions is an oxidation-reduction reaction? cuso4 + bacl2 yields baso4 + cucl2 agno3 + nacl yields agcl + nano3 pb(no3)2 + 2nacl yields pbcl2 + 2nano3 zn + h2so4 yields znso4 + h2

Which of the following elements is a representative element? a. chromium (cr) b. aluminum (al) c. mercury (hg) d. silver (ag)

Zoe is investigating the composition of substance a, an unknown substance. using chemical processes, she analyzes substance a and determines it is composed of sodium, oxygen, and hydrogen atoms in a ratio of 1 : 1 : 1. what is substance a? a. a compound b. an element c. a heterogeneous mixture d. a homogeneous mixture

What method(s) do plants use to obtain nitrogen? select all that apply. absorb it from the atmosphere use bacteria to convert nitrogen to usable form obtain usable nitrogen compounds from the soil absorb nitrogen from water taken in at the roots