4x Which of the following statements describes a difference between a mixture and a pure substance? dx A The density of a mixture can change with temperature, but the density of a pure substance cannot change. 4x B The composition of a mixture can vary from sample to sample, but the composition of a pure substance is always the same. C A mixture has a specific melting point, while the melting point of a pure substance can vary. D A mixture tends to be homogeneous, while a pure substance tends to be heterogeneous.

Convert 89000 g $Pb(NO_{3})_{2}$ to atoms

Given the following reactions and corresponding $\Delta H$ values, find the $\Delta H$ (to the nearest whole \#) for the reaction: $H_{2}SO_{4}(l)\rightarrow SO_{3}(g)+H_{2}O(g)$ $H_{2}S(g)+2O_{2}(g)\rightarrow H_{2}SO_{4}(l)$ $\Delta H=-235kJ$ $H_{2}S(g)+2O_{2}(g)\rightarrow SO_{3}(g)+H_{2}O(l)$ $\Delta H=-207kJ$ $H_{2}O(l)\rightarrow H_{2}O(g)$ $\Delta H=44kJ$ $\square $

Convert $4.68\times 10^{25}$ atoms $PBr_{3}$ to mol

Which of the following best describes a mixture? a material that is made up of many molecules a substance that can be changed into another substance a material that contains two or more substances a substance that has been broken down into Its smallest parts

What is used to of a hope of sixes in a a compound heard on the chermal reme? the periodic table prefixes chemical symbols the IUP AC

40. Using the hyphen form of symbol writing write the name of this atom. ${}_{9}^{19}F^{-1}$

Which of the following will not increase 1 point the rate of a chemical reaction? increasing surface area stirring decreasing the temperature increasing the concentration A __ is a substance that increases the rate of a reaction without being consumed. __ 1 point A(n) __ slows down the rate of a reaction. __ is a substance that 1 point

Use molecular orbital theory to determine the bond order in $H_{2}$ o 2 1 3

What is enthalpy? the heat absorbed or released during a phase change the heat content.of a system at constant pressure the heat absorbed during an endothermic reaction the heat given off during an exothermic reaction

1. What are two ways in which real gases differ from ideal gases? $\square $