HRS - Ask. Learn. Share Knowledge. Logo

Questions in chemistry

[Done] Complete the table: | Materials found at home | Phase of Matter | Use/s of the material/s at home | |------------------------|-----------------|--------------------------------| | Ex. water | liquid | Use for cooking, washing dishes and clothes, drinking, and taking a bath. | | 1. | | | | 2. | | | | 3. | | | | 4. | | | | 5. | | |

[Done] The value of Z for an atom containing 29 protons, 29 electrons, and 34 neutrons is: A. 58 B. 34 C. 29 D. 63 E. 5

[Done] Calculate the enthalpy of each reaction per mole of reactant using the formula below, which also converts joules to kilojoules. Record to 2 significant figures. [tex]$\Delta H=\frac{-q}{\text { moles }} * \frac{k J}{1000 J}$[/tex] Reaction 1: [ ] kJ/mol Reaction 2: [ ] kJ/mol

[Done] (A) Information about atom of some elements. | Element | Atomic number | No. of elements | No. of neutrons | No. of protons | Mass number | |---|---|---|---|---|---| | P | 7 | | | 7 | | | Q | 12 | | | | | | R | 13 | | | | | | S | 13 | | | | 27 | | T | | 15 | | | 30 | | U | | 18 | | 18 | | (i) Find and write values suitable for the places a, b, c, d, e, f. (ii) What is the element that belongs to group V in 3rd period? (iii) Name 2 isotopes among above elements. (iv) (a) Name the element with the lowest reactivity. (b) What is the reason for the lowest reactivity of that element? (B) Elements react with some other elements under various conditions. Among above elements: (a) Name the element that produces oxide and releases hydrogen gas by reacting with steam. (b) Sometimes after adding this element into hot water with a small amount of phenolphthalein, colourless water turns pink. (i) What is the element added to water? (ii) State whether that element is a metal or non-metal?

[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 (1/4).

[Done] Which statement best explains the change that occurs when gas particles move more slowly? A. The temperature increases because the average kinetic energy decreases. B. The temperature increases because the average kinetic energy increases. C. The temperature decreases because the average kinetic energy decreases. D. The temperature decreases because the average kinetic energy increases.

[Done] Consider the balanced equation below. [tex]4 NH_3+3 O_2 \rightarrow 2 N_2+6 H_2 O[/tex] What is the mole ratio of [tex]NH _3[/tex] to [tex]N _2[/tex]? A. 2:4 B. 4:2 C. 4:4 D. 7:2

[Done] Consider the following intermediate chemical equations: [tex] \begin{array}{l} C(s)+\frac{1}{2} O_2(g) \rightarrow CO(g) \ CO(g)+\frac{1}{2} O_2(g) \rightarrow CO_2(g) \end{array} [/tex] How will oxygen appear in the final chemical equation? A. [tex]O _2(g)[/tex] as a product B. [tex]O _2(g)[/tex] as a reactant C. [tex]O ( g )[/tex] as a product. D. [tex]2 O ( g )[/tex] as a reactant

[Done] What is the basic unit of matter? A. atom B. molecule C. gas D. compound

[Done] Consider the following intermediate chemical equations: [tex] \begin{array}{ll} NO(g)+O_3(g) \rightarrow NO_2(g)+O_2(g) & \Delta H_1=-198.9 kJ \\ \frac{3}{2} O_2(g) \rightarrow O_3(g) & \Delta H_2=142.3 kJ \\ O(g) \rightarrow \frac{1}{2} O_2(g) & \Delta H_3=-247.5 kJ \end{array} [/tex] What is the enthalpy of the overall chemical equation [tex]NO ( g )+ O ( g ) \rightarrow NO _2(g)[/tex] ? A. -305 kJ B. -304.1 kJ C. -93.7 kJ D. 5887 k . l