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Questions in chemistry

[Done] $2 Ca+O_2 \rightarrow 2 CaO$ The molar mass of each substance is provided in the table below. | Substance | Molar Mass (g/mol) | | :-------- | :----------------- | | Calcium $( Ca )$ | 40.08 | | Oxygen $\left( O _2\right)$ | 32.00 | | Calcium oxide $( CaO )$ | 56.08 | What mass of calcium is needed? $4.25 mol O _2$ $\square$ 2 $\square$ mol Ca 40.1 g Ca $=$ $\square$ g Ca 1 $mol O _2$ 1 mol Ca

[Done] Ammonia $\left( NH _3(g), \Delta H_{ f }=-45.9 kJ / mol \right)$ reacts with oxygen to produce nitrogen and water $\left( H _2 O ( g ), \Delta H_{ f }=-241.8\right. $kJ / mol$ ) according to the equation below. $4 NH_3(g)+3 O_2(g) \rightarrow 2 N_2(g)+6 H_2 O(g)$ What is the enthalpy of the reaction? Use $\Delta H_{\text {nan }}=\sum\left(\Delta H_{\text {f, products }}\right)-\sum\left(\Delta H_{\text {f, reectants }}\right)$. A. -3,572.1 kJ B. -1,267.2 kJ C. 1,267.2 kJ D. 3,572.1 kJ

[Done] Consider the following intermediate reactions: [tex] \begin{array}{ll} CH_4(g)+2 O_2(g) \rightarrow CO_2(g)+2 H_2 O(g) & \Delta H_1=-802 kJ \\ 2 H_2 O(g) \rightarrow 2 H_2 O(l) & \Delta H_2=-88 kJ \end{array} [/tex] The overall chemical reaction is as follows: [tex]CH_4(g)+2 O_2(g) \rightarrow CO_2(g)+2 H_2 O(l) \quad \Delta H_2=-890 kJ[/tex] What is the correct enthalpy diagram using Hess's law for this system? [tex]CH_2(a)+2 O_2(g)[/tex]

[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. $\Delta H=\frac{-q}{\text { moles }} * \frac{k J}{1000 J}$ Reaction 1: $\square$ $kJ / mol$ Reaction 2: $\square$ $kJ / mol$

[Done] Show the ions produced as each of the following salt molecules ionizes in body fluids: sodium chloride, potassium chloride, calcium chloride, magnesium chloride, and calcium carbonate.

[Done] How many moles of oxygen must be placed in a 3.00 L container to exert a pressure of 2.00 atm at [tex]$25.0^{\circ} C$[/tex]? Formula: [tex]$P V=n R T(R=0.0821 L \cdot atm / mol \cdot K )$[/tex] Which variables are given? pressure volume temperature moles

[Done] A. Choose the correct option(s) in each. 1. Which among the following is the cleanest fuel? (a) coal (b) petrol (c) diesel (d) CNG 2. Which coal produces the lowest amount of heat? (a) lignite (b) peat (c) anthracite (d) bituminous coal 3. Which of these is an example of a non-renewable resource? (a) trees (b) water (c) coal (d) grass 4. A natural fuel formed from deposits of carbon as plants decomposed millions of years ago. (a) coal (b) petroleum (c) natural gas (d) wood 5. Which of the following is a renewable energy resource? (a) solar (b) methane (c) crude oil (d) coal 6. What is the leading source of energy used in the United States today? (a) coal (b) oil resources (c) natural gas (d) nuclear power 7. Burning of which of the following fuels produces the least amount of carbon dioxide per unit of energy? (a) coal (b) oil (c) natural gas (d) all of these produce the same amount of carbon dioxide 8. Dead organisms are transformed into petroleum and natural gas in (a) absence of air (b) presence of air (c) presence of sunlight (d) none of these 9. Diesel is used in (a) cooking oil (b) paints (c) road surfacing (d) electric generators 10. Which of these is used in extraction of metals? (a) Coke (b) Coal gas (c) Coal tar (d) Petroleum 11. Which of these is used as solvent for dry cleaning? (a) Diesel (b) Kerosene (c) Petrol (d) Paraffin wax 12. The fibres manufactured by petrochemicals are (a) Nylon (b) Polyester (c) Acrylic (d) All of these B. Fill in the blanks: 1. Fuels which are formed by the decomposition of dead plants and animals are called ________. 2. The places where coal deposits are found are called ________.

[Done] In the laboratory, for the preparation of hydrogen gas from granular zinc, why can the following acids not be used? Which is the most suitable for this reaction? a. Conc H2SO4 b. Conc HCl c. HNO3

[Done] Based on the equation and the information in the table, what is the enthalpy of the reaction? [tex]\( \Delta H_{xn}=4619 kJ\)[/tex] [tex]\( \Delta H_{xn}=-46.19 kJ\)[/tex] [tex]\( \Delta H_{rxn}=92.38 kJ\)[/tex] [tex]\( \Delta H_{rxn}=-92.38 kJ\)[/tex]

[Done] Select the correct answer. An ion has a net charge of 3+. If this ion has 8 protons, how many electrons does it have? A. 3 B. 5 C. 7 D. 8 E. 11