HRS - Ask. Learn. Share Knowledge. Logo

Questions in chemistry

[Done] What is the mass of $CO_2$ in atomic mass units? A. 22 amu B. 12 amu C. 28 amu D. 44 amu

[Done] Select the correct answer. Polonium-210 decays once before it becomes a stable atom. What is that stable atom? [tex] {}_{84}^{210} Po \rightarrow \ldots+{ }_2^4 He [/tex] A. [tex] {}_{82}^{206} Pb [/tex] B. [tex] {}_{84}^{210} Po ^{-} [/tex] C. [tex] {}_{86}^{214} Rn [/tex] D. [tex] {}_{86}^{222} Rn [/tex] E. [tex] {}_{82}^{214} Pb [/tex]

[Done] (a) If M is a metal, then the litmus will turn ...... (b) If M is a non-metal, then the litmus will turn ...... (c) If M is a reactive metal, then ...... will be evolved when M reacts with dilute sulphuric acid. (d) If M is a metal, it will form ...... oxide, which will form ...... solution with water. (e) If M is a non-metal, it will not conduct electricity in the form of ......

[Done] Consider the following intermediate chemical equations: [tex]$\begin{array}{l} 2 Na(s)+Cl 2(g) \rightarrow 2 NaCl(s) \ 2 Na_2 O(s) \rightarrow 4 Na(s)+O_2(g) \end{array}$[/tex] In the final chemical equation, NaCl and [tex]$O _2$[/tex] are the products that are formed through the reaction between [tex]$Na _2 O$[/tex] and [tex]$Cl _2$[/tex]. Before you can add these intermediate chemical equations, you need to alter them by A. multiplying the second equation by 2. B. multiplying the first equation by 2. C. multiplying the first equation by (1/2). D. multiplying the second equation by ([tex]$1 / 4$[/tex]).

[Done] Which fire extinguisher should only be used in a well-ventilated area? A. Class B B. Class C C. Class D D. Class A

[Done] Use your understanding of the ideal gas law to identify the correct relationships among the variables. Pressure is inversely related to volume Temperature is inversely related to moles Volume is inversely related to pressure Moles are inversely related to temperature Identify the ideal gas law equation.

[Done] Which of these are examples of physical changes? Check all that apply. burning wood freezing water cutting paper iron rusting mixing water and acetone

[Done] An isotope with 15 protons and 17 neutrons will have which symbol? A. ${}_{15}^{17} Cl$ B. ${}_{15}^{17} P$ C. ${}_{17}^{32} Cl$ D. ${}_{17}^{32} P$ E. ${}_{15}^{32} P

[Done] Type the correct answer in the box. Express your answer to three significant figures. The half-life of carbon-14 is 5,730 years. Dating organic material by looking for [tex]$C -14$[/tex] can't be accurately done after 50,000 years. Suppose a fossilized tree branch originally contained 4.30 grams of C-14. How much C-14 would be left after 50,000 years? Use the formula [tex]$N=N_0\left(\frac{1}{2}\right)^{\dagger}$[/tex]. A tree branch that originally had 4.3 grams of carbon-14 will have $\square$ grams after 50,000 years.

[Done] Match the words, definitions, and examples: Element Molecule Compound Mixture Two or more atoms chemically joined together Two or more different atoms chemically joined together A substance made from only one type of atom Different elements, molecules or compounds not chemically joined together