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Questions in chemistry

[Terjawab] " $Na _2 SO _3$ " represents sodium sulfite. What does the 4 mean in the formula $4 Na _2 SO _3$ ? A. There are four atoms of sodium. B. There are four atoms of sodium sulfite. C. There are four molecules of sodium sulfite. D. There are four elements in sodium sulfite.

[Terjawab] What is the atomic mass of oxygen-18?

[Terjawab] Which reaction is an example of a balanced endothermic reaction? Answer Options: Select one of four $N_2(g)+O_2(g)-\text { heat } \rightarrow 2 NO(g)$ $N_2(g)+O_2(g)+\text { heat } \rightarrow 2 N(g)$ $N_2(g)+O_2(g)+\text { heat } \rightarrow 2 NO(g)$ $N_2(g)+O_2(g) \rightarrow 2 NO(g)$

[Terjawab] What's missing from this chemical reaction that shows the combustion of propane? [tex]C _3 H _8+ O _2 \rightarrow H _2 O + CO _2[/tex] Answer Options: A. Methane as a secondary product B. The release of heat with the products C. An intermediary transition to butane D. The absorption of heat by the reactants

[Terjawab] What is the average atomic mass of the element in the data table? | Mass (amu) | Abundance (%) | | :---------- | :------------- | | 35.0 | 75.77 | | 37.0 | 24.23 | A. 63.9 amu B. 21.0 amu C. 41.2 amu D. 35.5 amu

[Terjawab] solid $A+$ water $\longrightarrow$ saturated solution At $60^{\circ} C 24g+100 g \rightarrow 124 g$ At $60^{\circ} C$ 100g of water is mixing 124 g solid $=30 g$ of water saturate? $\begin{array}{l} =\frac{30g \times 124g}{100g} \\ =37.2g \end{array}$

[Terjawab] For a certain chemical reaction, the standard Gibbs free energy of reaction is -67.5 kJ. Calculate the temperature at which the equilibrium constant [tex]K=2.8 \times 10^{12}[/tex]. Round your answer to the nearest degree.

[Terjawab] How many grams of nitrogen are in 3.51 mol N? [?] g N

[Terjawab] You have a cream containing 0.5% w/w calamine. What amount of hydrocarbon is needed such that when requested to add to this cream, it will be 70.0% w/w? What is the concentration of hydrocarbon in the new cream?

[Terjawab] a) What is the name for the structure of an ionic compound as shown in the diagram? ​