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Questions in chemistry

[Answered] The label on a gas cylinder will tell you... A. the molecular weight of the gas. B. the name of the gas. C. the hazards associated with the gas. D. Both B and C are correct. E. All of the above are correct.

[Answered] How many moles of [tex]$O_2$[/tex] gas react with 2 moles of NO gas according to the following balanced chemical equation? [tex]2 NO(g)+O_2(g) \longrightarrow 2 NO_2(g)[/tex] A. [tex]$2 mol O_2$[/tex] B. [tex]$4 mol O_2$[/tex] C. [tex]$1 mol O_2$[/tex] D. [tex]$0.5 mol O_2$[/tex] E. none of the above

[Answered] A molecule contains 18 atoms and undergoes a physical change. How does the physical change affect the total number of atoms of each element? A. It remains the same. B. It increases C. It changes to zero. D. It decreases

[Answered] What criteria are used to classify fires? A. The type of materials that are on fire (what is fueling the fire) B. The size of the fire and how fast it is spreading C. The location of the nearest fire extinguisher D. All of the above

[Answered] A radioactive nuclide that is used to label blood platelets has 49 protons and 62 neutrons. Which is the symbol of this nuclide? ${ }_{62}^{49} \ln$ ${ }_{49}^{62} \ln$ ${ }_{111}^{49} \ln$ ${ }_{49}^{111} \ln

[Answered] What are homogeneous mixtures of metals commonly called? A. alloys B. colloids C. compounds D. suspensions

[Answered] Which of these compounds is a weak electrolyte? NaCl [tex]$C _6 H _{12} O _6$[/tex] (glucose) [tex]$O _2$[/tex] [tex]$CH _3 COOH$[/tex] (acetic acid) HCI

[Answered] What volume of ethanol (density $=0.7893 g / cm ^3$ ) should be added to 450. mL of water in order to have a solution that freezes at $-15.0^{\circ} C$ ? Assume the density of water is $1.0 g / mL$. (For water, $K_f=1.86^{\circ} C / m$.) A. 470 mL B. 167 mL C. 371 mL D. 212 mL E. 132 mL

[Answered] What is a reaction rate? A. The amount of products produced in a reaction B. The frequency of reactant collisions C. The energy required for a reaction to happen D. The speed at which a reaction occurs

[Answered] A) [tex]$C + O _2 \longrightarrow CO _2$[/tex] [tex]$BN _2+ O _2 \rightarrow 2 NO$[/tex] C) [tex]$Zn +2 HCl \longrightarrow ZnCl _2+ H _2$[/tex] D) [tex]$CaO + H _2 O \longrightarrow Ca ( OH )_2$[/tex] Short answer type questions: a. What are reactants and products? b. What is a balanced chemical equation? c. Write down the balanced chemical equation of the reaction between zinc and hydrochloric acid. What type of chemical reaction is this? d. What is endothermic reaction?